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This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A car is moving towards North. What will be the direction of force of friction acting on this car due to surface of road ? |
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Answer» The direction of force of friction acting on this car due to surface of road is along the south direction i.e. opposite to the direction of motion. |
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| 52. |
You spill a bucket of soapy water on a marble floor accidently. Would it make easier or more difficult for you to walk on the floor? Why? |
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Answer» It will make more difficult to walk on the floor. As soapy solution decreases the friction on the floor. |
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| 53. |
An object of mass m slides down a hill of height h and of arbitrary shape and stops at the bottom because of friction. The coefficient of friction may be different for different segments of the path. Work required to return the object to its position along the same path by a tangential force is |
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Answer» Correct Answer - 2 mgh |
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| 54. |
A railroad flat car is loaded with crates with coefficient of friction 0.25 with the car. It the car is moving at 30 kmph, in what is the shortest distance over which the car can be stopped without letting the crates slide ? |
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Answer» Correct Answer - 14.16 m |
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| 55. |
A block of mass `m` height `2h` and width `2b` rests on a flat car which moves horizontally with constant acceleration a as shown in figure. Determine a. the value of the acceleration at which slipping of the block on the car starts, if the coefficient of friction is `mu`. b. the value of the acceleration at which block topples about `A`, assuming sufficient friction to prevet slipping and c. the shortest distance in which it can be stopped from a speed of `20 ms^(-1)` with constant deceleration so that the block is not disturbed. The following data are given `b=0.6 m, h=0.9 mu=0.5` and `g=10ms^(-2)` |
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Answer» Correct Answer - `mug, (cg)/(h)` |
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| 56. |
A body of mass 4kg rests in limiting equilibrium on a rouch plane whose slope is `30^(@)`. The slope is subsequently increased to `60^(@)`. Calculate (i) coefficient of limiting friction between the body and the surface, (ii) acceleration down the plane if coefficient of kinetic friction is 0.4, (iii) force required to prevent it from sliding down the plane, (iv) force required to just move it up the plane. `(g = 9.8 m//s^(2))`. |
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Answer» Correct Answer - (i) 0.5774 (ii) `6.53 ms^(-2)` (iii) 22.63 N (iv) 45.26 N |
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| 57. |
A given object taken n time more time to slide down `45^(@)` rough inclined plane as it taken to slide down a perfectly smooth `45^(@)` incline The coefficient of kintic friction between the object and the incline is .A. `(1-(1)/(n^(2)))`B. `(1)/(1-n^(2))`C. `sqrt((1-(1)/(n^(2))))`D. `sqrt((1)/(1-n^(2)))` |
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Answer» Correct Answer - A |
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| 58. |
A motorcycle is travelling on a curved track of radius 500 m. If the coefficient of friction between road and tyres is 0.5, the speed avoiding skidding will beA. 50 m/sB. 75 m/sC. 25 m/sD. 35 m/s |
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Answer» Correct Answer - A |
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| 59. |
Assuming the coefficient of friction between the road and tyres of a car to be 0.5, the maximum speed with which the car can move round a curve of 40.0 m radius without slipping, if the road is unbanked, should beA. 25 m/sB. 19 m/sC. 14 m/sD. 11 m/s |
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Answer» Correct Answer - C |
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| 60. |
Consider a car moving along a straight horizontal road with a speed of 72 km / h . If the coefficient of kinetic friction between the tyres and the road is 0.5, the shortest distance in which the car can be stopped is `[g=10ms^(-2)]`A. 30 mB. 40 mC. 72 mD. 20 m |
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Answer» Correct Answer - B |
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| 61. |
A car is moving along a stight horizontal road with a speed `v_(0)` . If the coefficient of friction between the tyres and the road is mu, the shortest distance in which the car can be stopped is.A. `(v_(0)^(2))/( 2mu g)`B. `(v_(0))/( mu g)`C. `((v_(0))/(mu g))^(2)`D. `(v_(0))/(mu)` |
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Answer» Correct Answer - A `0 = v_(0)^(2) - 2mu gs rArr s = (v_(0)^(2))/( 2mu g)` |
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| 62. |
A vehicle of mass `M` is moving on a rough horizontal road with a momentum P If the coefficient of friction between the tyres and the road is `mu` is then the stopping distance is .A. `(P)/(2mumg)`B. `(P^(2))/(2mumg)`C. `(P)/(2mum^(2)g)`D. `(P^(2))/(2mum^(2)g)` |
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Answer» Correct Answer - D |
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| 63. |
A block rests on a rough inclined plane making an angle of `30^(@)` with horizontal. The coefficient of static friction between the block and inclined plane is `0.8` . If the frictional force on the block is `10 N`, the mass of the block in `kg` is `(g = 10 m//s^(2))`A. `2.0`B. `4.0`C. `1.6`D. `2.5` |
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Answer» Correct Answer - A |
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| 64. |
A body of mass 5 kg rests on a rough horizontal surface of coefficient of friction 0.2. The body is pulled through a distance of 10 m by a horizontal force of 25 N . The kinetic energy acquired by it is `(g=10ms^(2))`A. 330 JB. 150 JC. 100 JD. 50 J |
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Answer» Correct Answer - B |
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| 65. |
if `mu_(s),mu_(k)` and `mu_(r)` are coefficeints of static friction, sliding friction and rolling friction, then.A. `mu_(s) lt mu_(k) lt mu_(r)`B. `mu_(k) lt mu_(r) lt mu_(s)`C. `mu_(r) lt mu_(k) lt mu_(s)`D. `mu_(r)=mu_(k)=mu_(s)` |
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Answer» Correct Answer - C |
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| 66. |
While walking on ice, one should take small steps to avoid slipping. This is because smaller steps ensure (a) larger friction (b) smaller friction (c) larger normal force (d) smaller normal force. |
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Answer» (b) smaller friction Explanation: Small steps keep the angle between the leg and the vertical small i.e. angle between the contact force and vertical is small so the horizontal component of the contact force (Friction force) is small. |
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| 67. |
While walking on ice, one should take small steps to avoid sliping. This is because smaller steps ensureA. larger frictionB. smaller frictionC. larger normal forceD. smaller normal force |
| Answer» Correct Answer - B | |
| 68. |
Explain why sliding friction is less than static friction. |
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Answer» When an object starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly less than the static friction. |
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| 69. |
To avoid slipping while walking on ice, one should take smaller steps because of theA. Friction of ice is largeB. Larger normal reactionC. Friction of ice is smallD. Smaller normal reaction. |
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Answer» Correct Answer - C |
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| 70. |
A box is lying on an inclined plane what is the coefficient of static friction if the box starts sliding when an angle of inclination is `60^(@)`A. 1.173B. 1.732C. 2.732D. 1.677 |
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Answer» Correct Answer - B |
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| 71. |
Two objects A and B are thrown upward simultaneously with the same speed. The mass of A is greater than the mass of B. Suppose their exerts a constant and equal force of resistance on the two bodies.A. The two bodies will reach the same height.B. `A` will go higher than `B`.C. `B` will go higher than `A`.D. Any of the above three may happen dependending on the speed with which the objects are thrown. |
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Answer» Correct Answer - B `A : 0 = u^(2) - 2(g + (R )/(m_(A))) h_(A)` (i) `B : 0 = u^(2) - 2 (g + (R )/(m_(B))) h_(B)` (ii) `(h_(A))/(h_(B)) = ( g + (R )/(m_(B)))/(g + (R )/(m_(A)))` Since `m_(A) gt m_(B) , (R )/(m_(A)) lt (R )/(m_(B))` `(g + (R )/(m_(A))) lt (g + (R )/(m_(B)))` `h_(A) gt h_(B)` |
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| 72. |
Hypothesis: The sole of shoe’s grave is to provide better grip on the floor. Reason: Friction is caused by the irregularities on the two surface those are in contact.A) Hypothesis is correct. Reason is correct explanation of hypothesis. B) Hypothesis is correct. Reason is not correct explanation of hypothesis C) Hypothesis is not correct and reasons are correct D) Both hypothesis and reasons are not correct |
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Answer» A) Hypothesis is correct. Reason is correct explanation of hypothesis |
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| 73. |
A brick of mass 2kg begins to slide down on a plane inclined at an angle of `45^(@)` with the horizontal. The force of friction will beA. `19.6sin45^(@)`B. `19.6cos45^(@)`C. `9.8sin45^(@)`D. `9.8cos45^(@)` |
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Answer» Correct Answer - A |
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| 74. |
A body takes just twice the time as long to slide down a plane inclined at `30^(@)` to the horizontal as if the plane were frictionless. The coefficient of friction between the body and the plane isA. `(sqrt(3))/(4)`B. `sqrt(3)`C. `(4)/(3)`D. `(3)/(4)` |
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Answer» Correct Answer - A |
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| 75. |
Maximum value of static friction is .A. Limiting frictionB. Rolling frictionC. Normal reactionD. Coefficient of friction |
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Answer» Correct Answer - A |
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| 76. |
Understanding the principle of ball bearings.Take two lids and rotate them by putting one on the top of the other.a) What do you observe?b) What do you observe?c) What is your conclusion on the principle of ball bearings? |
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Answer» a) It is difficult to rotate them. Now place three to four marbles on one lid and place the other lid on the top of the marble. Now try to rotate the top lid. b) Now we can easily rotate the lid because rolling friction is less than sliding friction. c) We can easily rotate top lid by placing marbles between the lids. This is the principle of ball bearings. |
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| 77. |
Pulling force making an angle `theta` to the horizontal is applied on a block of weight `W` placed on a horizontal table. If the angle of friction is `alpha`, then the magnitude of force is `alpha` , then the magnitude of force required to move the body is equal toA. `(Wsinalpha)/(gtan(theta-alpha))`B. `(Wcosalpha)/(cos(theta-alpha))`C. `(Wsinalpha)/(cos(theta-alpha))`D. `(Wtanalpha)/(sin(theta-alpha))` |
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Answer» Correct Answer - C |
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| 78. |
Water from the bottom of a dam of depth `h` comes out through a narrow pipe and strikes continuousy the tips of the blades of a water turbine. The length of each blade is R. Calculate the most advantaneous speed of rotation of the turbine [Hint : The most advantageous speed corresponds to the development of maximum power in the turbine] |
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Answer» Correct Answer - `sqrt(2gh)//3R` |
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| 79. |
Class 8 Science MCQ Questions of Friction with Answers? |
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Answer» lass 8 Science MCQ Questions of Friction with Answers for a significant piece of exam for Class 8 Science and whenever practiced appropriately can assist you with getting better grades. Refer to more Chapter-wise MCQ Questions for Class 8 Science and furthermore check out more most recent study material for all subjects. MCQ Questions for Class 8 Science with Answers were arranged dependent on the most recent Exam Pattern, Syllabus, NCERT curriculum. We have given MCQ Questions to Class 8 with answers to assist understudies with understanding the idea well indeed. These MCQ Questions for Class 8 Friction will allow students a chance to test their knowledge and also prepare for the examination. Practice Class 8 Science MCQ Questions chapter-wise 1. Friction is a (a) non-contact force 2. Which of the following produces the least friction? (a) Sliding friction 3. Friction always (a) opposes the motion 4. Friction can be reduced by using (a) oil 5. Static friction is less than (a) sliding friction 6. Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play (a) only if the objects are solid. 7. To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable? (a) Stone 8. The shape of an aeroplane is like a (a) dog 9. Friction due to fluids is called (a) force 10. Which of the following is not a smooth surface? (a) Surface of wet soap 11. A toy car released with the same initial speed will travel farthest on (a) muddy surface 12. If we apply oil on door hinges, the friction will (a) increase 13. Lubricant can (a) reduce friction 14. Force of friction depends on (a) roughness of surface 15. Which is a streamlined object? (a) Boats 16. Smooth surface has (a) less friction 17. Which of the following is responsible for wearing out of bicycle tyres? (a) Muscular force 18. Tyres are treaded to (a) look good 19. Four children were asked to arrange forces due to rolling, static and sliding frictions in decreasing order. Their arrangements are given below. (a) Rolling, static, sliding 20. A matchstick catches fire when struck against the side of the matchbox because: (a) of the chemicals 21. Talcum powder should not be spilled on the floor of the room because: (a) it will stain the floor 22. Gymnasts apply some coarse substance on their hands to: (a) increase friction for better grip 23. Ball-bearing are used to reduce friction by (a) Applying lubricants to the balls used 24. To convert the static, sliding friction into rolling friction, the heavy luggage carriers are attached at their base. (a) ball-bearings 25. Friction produces (a) Motion Answer: 1. Answer: (b) contact force Explanation: Friction is a contact force because the bodies need to get in contact with each other in order for the frictional force to act on the bodies. 2. Answer: (b) Rolling friction Explanation: Rolling friction produces the least friction. 3. Answer: (a) opposes the motion Explanation: Frictional force acts between two surfaces in contact. It stops the object from moving as the irregularities on both the surface lock into each other, thus obstructing any forward motion. Hence, frictional force always opposes the applied force. 4. Answer: (d) all of these Explanation: Friction can be described as an opposing force that resists other forces such as rolling, sliding.Friction can be reduced by adding lubricants such as grease, oil or powder.Polishing surfaces can also reduce friction.Friction is the leading cause of surface roughness. 5. Answer: (d) none of these Explanation: Static friction is strongest, followed by sliding friction, and then rolling friction, which is weakest. 6. Answer: (d) irrespective of whether the objects are solid, liquid or gaseous Explanation: Friction occurs irrespective of state of the matter. Friction provided by liquids and gases are known as fluid friction. 7. Answer: (a) Stone Explanation: Stone will be more suitable because it will exert greater reaction and hence greater friction force which sharpen the blade of a knife easily by rubbing. 8. Answer: (b) bird Explanation: Aeroplanes have been designed as birds. Birds have a light body, shaped such as to have a minimum wind resistance when they fly to overcome the friction. Thus, aeroplanes have been designed such as to have a streamlined body to overcome the frictional force of air. 9. Answer: (d) drag Explanation: This frictional force is called drag force, and this parallels the motion of the body in a fluid medium. Hence option D is the correct answer and as per this frictional force exerted by fluids is called drag. 10. Answer: (b) Surface of tyres Explanation: As we know that the surface of tyres is rough and uneven so we can say that the surface of a tyre is not a smooth surface. 11. Answer: (b) polished marble surface Explanation: Because a polished marble floor has the least frictional force and inertia, a car will move farthest on it. 12. Answer: (b) decrease Explanation: When we put the oil the rough interlocks between the surface and body are filled by the drops of oil and hence become smooth and then the friction decreases. So, here we can say that if we apply oil on door hinges, the friction will decrease. 13. Answer: (a) reduce friction Explanation: Lubricants are substances which reduce friction. 14. Answer: (d) all of these Explanation: Friction depends partly on the smoothness of the contacting surfaces, a greater force being needed to move two surfaces past one another if they are rough than if they are smooth. 15. Answer: (d) all of these Explanation: Streamlined objects would include objects that are designed to travel quickly and create a minimum of friction against either air or water. Some objects that are streamlined include trains, airplanes, space shuttles, rockets, boats, submarines, racing cars, racing boats, and even televisions. 16. Answer: (a) less friction Explanation: Friction is less on a smooth surface, hence the roller travels a greater distance on a smooth surface compared with the rough surface 17. Answer: (c) Frictional force Explanation: Frictional force is responsible for wearing out of bicycle tyres. 18. Answer: (b) Increase friction Explanation: The tyres of cars, trucks and bulldozers have treads or grooves in the rubber which is designed to allow water to be expelled from beneath the tire. This provides better grip with the ground thereby increasing friction for better handling. 19. Answer: (c) Static, sliding, rolling Explanation: Sliding friction is the force of friction, below two objects when one of them is sliding over the surface of the other. The force of sliding friction between them is a little smaller than static friction between them. Between the same two surfaces, once motion is started the friction becomes slightly less than maximum static force rolling friction - a force of friction that comes into play when one body rolls over the surface of another body.It is more convenient to roll then to slide an object once the surface of other Hence, static friction > sliding friction > Rolling friction. 20. Answer: (c) friction produces a spark and the Explanation: A matchstick catches fire when struck against the side of the matchbox because friction produces a spark and the chemicals catch fire. 21. Answer: (b) it may cause us to slip and fall Explanation: Friction is a force that only occurs when an object moves. Talcum powder should not be spilled on the floor of room because it may cause us to slip and fall. 22. Answer: (a) increase friction for better grip Explanation: Gymnasts apply the coarse substance on their hands to increase friction for a better grip. The coarse substance is chalk powder. The powder increases the friction between the bar and the gymnast's hands. It also absorbs sweat from the hands and keeps it dry for a better grip. 23. Answer: (c) Reducing the area of contact with the use of metallic balls Explanation: Ball bearing reduce friction by using smooth balls lubricated with oil or grease that freely roll between a smooth inner and outer surface. The area of contact between the inner and outer surface decreases hence friction decreases between them. 24. Answer: (d) wheels Explanation: To convert the static, sliding friction into rolling friction, the heavy luggage carriers are attached with wheels at their base, wheels decrease the friction. The decreasing order is static, sliding, and rolling 25. Answer: (c) Heat Explanation: Friction always slows a moving object down. The amount of friction depends on the materials from which the two surfaces are made. The rougher the surface, the more friction is produced. Friction also produces heat Click here Practice MCQ Question for Friction Class 8 |
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| 80. |
A block of mass 5kg is on a rough horizontal surface and is at rest. Now a force of 24 N is imparted to it with negligible impulse. If the coefficient of kinetic friction is 0.4 and g=9.8m//s^(2)` , then the acceleration of the block isA. `0.26m//s^(2)`B. `0.39m//s^(2)`C. `0.69m//s^(2)`D. `0.88m//s^(2)` |
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Answer» Correct Answer - D |
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| 81. |
Opposite to acceleration is A) deceleration B) retardationC) negative acceleration D) all of these |
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Answer» D) all of these |
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| 82. |
If you push a ball which is in the rest on a ground, then its speed A) first increases, then decreases B) first increases, then remains constant C) first decreases, then increases D) first decreases, then come to rest |
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Answer» A) first increases, then decreases |
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| 83. |
Which force is responsible for the wearing out of car tyres? |
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Answer» Frictional force is responsible the wearing of car tyres. |
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| 84. |
The Mction exerted by a rolling body is A) static friction B) sliding friction C) rolling friction D) none of these |
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Answer» C) rolling friction |
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| 85. |
………… is responsible for over heating and wearing out of moving parts. A) Normal force B) Friction C) Tension D) Gravitational force |
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Answer» Correct option is B) Friction |
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| 86. |
Which of the following is easy to push? A) A brick in horizontal position B) A brick in vertical position C) Both are equal to push D) We cannot say |
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Answer» C) Both are equal to push |
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| 87. |
Gymnasts apply which material on their hands to increase Motion for better grip? A) oil B) soaps C) coarse substance D) water |
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Answer» C) coarse substance |
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| 88. |
Why do Gymnasts apply some coarse substance on their hands? |
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Answer» Gymnasts apply some coarse substance on their hands to increase friction for better grip. |
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| 89. |
What is the effect of area of contact on frictional force? |
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Answer» Frictional force is independent of area of contact. |
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| 90. |
In what direction does frictional force act when a body moves on the surface of another body? A) In the direction of motionB) In the direction opposite to motion C) Perpendicular to direction of motion D) Frictional force does not have direction |
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Answer» B) In the direction opposite to motion |
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| 91. |
The fish swim easily in water because by A) More energy B) Streamlined shape C) Both (A) and (B) D) None of the above |
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Answer» B) Streamlined shape |
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| 92. |
Portars use Thalapaga (bundle of cloth) (turban) on their heads while carrying luggage this provides A) more friction B) less friction C) more pressure D) less pressure |
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Answer» D) less pressure |
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| 93. |
The body is not moving, then the Motion isA) 30 N (→) B) 30 N (←) C) 50 N (→) D) 50 N(←) |
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Answer» Correct option is A) 30 N (→) |
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| 94. |
When person cycling on rough horizontal surface then which of the following are correctA. Friction on front wheel is towards leftB. Friction on front wheel is towards rightC. Friction on rear wheel towards rightD. Friction on rear wheel towards left |
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Answer» Correct Answer - A::C Friction is opposite to direction of relative motion. |
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| 95. |
A body is moving down a long inclined plane in inclination `45^(@)` with horizontal. The coefficient of friction between the body and the plane varies as `mu=x//2`, where `x` is the distance moved down the plane. Initially `x=0 & v=0`.A. When `x=2` the velocity of the body is `sqrt(gsqrt(2))m//s`B. The velocity of the body increases all the timeC. At an instant when `v!=0` the instantaneous acceleration of the body down the plane is `(g(2-x))/(2sqrt(2))`D. The body first accelerates and then decelerates |
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Answer» Correct Answer - A::C::D When `v cancel=0` the aceeleration is `vec(a)_("inst") = (1)/(m)(mg sin theta-mu mg cos theta)` `= g(sin theta-(x)/(2) cos theta)-(g(2-x))/(2sqrt(2))` `rArr v(dv)/(dx) = (g)/(2sqrt(2))(2-x)` `rArr underset(0)overset(v)int v dv = (g)/(2sqrt(2))[2x-(x^(2))/(2)]_(0)^(2) rArr v = sqrt(gsqrt(2))m//s` Also it is clear that for `x lt 2` the body accelerates, at `x = 2` the acceleration is zero and for `x gt 2` the body retards till it comes to rest. |
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| 96. |
A block of mass `2 kg` is placed on the floor of an elevator. The elevator is moving with an acceleration of `6hat(i)+7hat(j)m//s^(2)`. If `●=0.5, g =10ms^(-2)` and horizontal, vertically upward direactions are taken as `+ve x,y` axes, find frictional force actiong on the block.A. `12 N`B. `16 N`C. `10 N`D. `17 N` |
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Answer» Correct Answer - A Normal force `N=m[g+a_(y)]=2[10+7]=34N` limiting friction `f_(L)=* N=0.5xx34=17N` horizontal force on the block `f = m xx a_(x) = 2 xx 6 = 12`. As `f lt f_(L)`, block will be at rest w.r.t. elevator and the friction is `12 N` only. |
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| 97. |
A box is placed on an inclined plane and has to be pushed down.The angle of inclination isA. equal to angle of frictionB. more than angle of frictionC. equal to angle of reposeD. less than angle of repose |
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Answer» Correct Answer - D `mu mg cos theta gt mg sin theta` `mu gt tan theta` `tan alpha gt tan theta` `alpha gt theta ,alpha : angle of friction` When the block is about to move on rough inclined plane , angle of friction = angle of repose |
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| 98. |
The friction between two surfaces does not depend on one of the following. This one is:A. amount of surface area of the two objects which is in contact with each other B. weight of the object which tends to move on the surface of other object C. degree of smoothness of surfaces of two objects in contact with each other D. degree of roughness of surfaces of two objects in contact with each other |
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Answer» A. amount of surface area of the two objects which is in contact with each other Friction does not depend on the area of contact. |
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| 99. |
A big wooden box is being pushed on the ground from east to west direction. The force of friction due to ground will act on this box towards: A. north direction B. south direction C. east directionD. west direction |
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Answer» D. west direction The force of friction acts opposite to the direction of motion. |
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| 100. |
Give the name of material which reduces the force of friction. |
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Answer» Lubricant is the name of the material which is used to decrease the amount of friction between two surfaces in contact. It is a liquid or type of oil actually. |
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