Explore topic-wise InterviewSolutions in Current Affairs.

B) Convex mirror

(c) C_p is slightly greater than C_v

The correct answer is (b) 50calories

Correct option is B) II, III

The correct answer is (b) 0.5% 

The correct answer is (c) C_p - C_v

• Solar devices like solar cooker or solar water heater use solar energy to cook food or heat water. 
• When sun rays fall on the concave mirror, they converge and come together in the focal plane.
• Due to convergence, the intensity of sun rays increases and the food or water is heated faster. Hence, concave mirrors are used in solar- devices.

The correct answer is (d) Q = W

(a) Torch light: The source of light is placed at the focus. 

(b) Projector lamp : The source of light is placed at the centre of curvature. 

(c) Flood light : The source of light is placed just beyond the centre of curvature.

The answer is: (b) \(\sqrt3+\sqrt{19}\)

The only retarding force that acts on him, if he is not using a seat belt comes from the friction exerted by the seat. This is not enough to prevent him from moving forward when the vehicle is brought to a sudden halt.

Correct answer is C.

So, the area enclosed from x = 1 to x = x (say) is (x – 1) sin (3x + 4)

⇒ A = ∫f(x) dx = F(x) = (x – 1) sin (3x + 4)

⇒ f(x) = F’(x) = sin (3x + 4) + 3(x – 1) cos (3x + 4)

(Using u-v rule of differentiation)

प्रश्नानुसार, द्विआधारी संक्रिया समुच्चय N पर इस प्रकार परिभाषित की गयी है कि a * a = a, ∀ a ∈ N 

(i) यहाँ पर * संक्रिया में केवल एक ही अवयव का प्रयोग किया गया है। अत : स्पष्ट है कि यह कथन असत्य है। 

(ii) वास्तविक संख्याओं में समुच्चय पर संक्रिया * क्रमविनिमेय है। 

b * c = c * b

∴ तथा (c * b) * a = (b * c) * a = a * (b * c)

∴ a* (b * c) = (c * b) * a

∴ यह कथन सत्य है।

CA -pathway is an alternative photosynthetic pathway seen in plants like sugarcane/sorghum/ maize in which the1ststable compound is oxaloacetate a 4-C compound. It is called Hatch-slack pathway.

(a) विद्युत-क्षेत्र रेखा वह वक्र है जिसके प्रत्येक बिन्दु पर खींची गई स्पर्श रेखा उस बिन्दु पर विद्युत-क्षेत्र की दिशा को प्रदर्शित करती है। ये क्षेत्र रेखाएँ सतत वक्र होती हैं अर्थात् किसी बिन्दु पर एकाएक नहीं टूट सकतीं, अन्यथा उस बिन्दु परे विद्युत-क्षेत्र की कोई दिशा ही नहीं होगी, जो असम्भव है। 

(b) दो विद्युत-क्षेत्र रेखाएँ एक-दूसरे को प्रतिच्छेदित नहीं कर सकतीं; क्योंकि इस स्थिति में कटान बिन्दु पर दो स्पर्श रेखाएँ खींची जाएँगी जो उस बिन्दु पर विद्युत-क्षेत्र की दो दिशाएँ प्रदर्शित करेंगी जो असम्भव है।

u = √((5)² + (12)² )= 13 ms^-1.

Correc Option is (D) 900 \(kmh^{-1}\)

\(v_p = -500\) km/h

\(V_{gp} = 1400\) km/h

The speed of burnt gas with respect to the jet airplane is

\(\overrightarrow v_{gp} = \overrightarrow v_g - \overrightarrow v_p\)

\(1400 = v_g + 500\)

\(v_g = 1400 - 500\)

\(v_g = 900\) km/h

Correct option is: (D) 900 kmh^-1

The pineal body secretes the hormone Melatonin which regulates sleep and wake cycle.

Motion of a body along a circular path with constant speed is called uniform circular motion.

When the angle of projection is 45° the range of a projectile is maximum.

(d) Pineal body

An athlete must throw shot – put or a javelin approximately at an angle 45°to achieve the maximum range.

Cerebro spinal fluid

Correct option is: (D) [M⁰L⁰T⁰]

The given relation is E = \(\frac{b-x^2}{a}\)

As x is subtracted from b,

∴ dimensions of b are x²;

i.e., b = [L²]

∴ We can write equation as E = \(\frac{L^2}{a}\)

Or a = \(\frac{L^2}{E}\) = \(\frac{L^2}{[L^2MT^{-2}]}\) = [L⁰M^-1T²]

Ratio of masses of two planets is 

m₁ : m₂ = 2 : 3 

Ratio of their radii, R₁ : R₂ = 4 : 7 

We know g 

Img 2 

∴ g₁ : g₂ = 49 : 24

t = 1.2 s; u = 1.8 m/s; v = 4.2 m/s

acceleration a = \(\frac{v-u}{t}\)

= \(\frac{4.2 - 1.8}{1.2}\) = \(\frac{2.4}{1.2}\)

= 2 m/s²

Now, the force applied is the same, it will produce the same acceleration.

Change in speed = acceleration x time for which force is applied.

= 2 x 2 = 4 m/s

change in speed = 4 m/s.

(a) For t < 0. No force as Particles is at rest. For t > 4s, No force again particle comes at rest. 

For 0 < t < 4s, as slope of OA is constant so velocity constant i.e ., a = 0,  so force must be zero.

(b) Impulse at t = 0

Impulse = change in momentum

I = m(v - w) = 4(0 - 0.75) = 3kg ms^-1

Impulse at t = 4s

1 = m(v - u) = 4 (0 - 0.75) = -3 kg ms^-1

The momentum of an object is defined as the product of its mass and velocity.

The product of mass and velocity of a moving body gives the magnitude of linear momentum. It acts in the direction of the velocity of the object. 

Its S.I unit is kg ms^-1.

Due to inertia of motion.

Correct answer is (c) \(a = \frac{F}{m_1 + m_2}\) 

(c) greater than 1

Correct answer is (b) F

Case (a) :

a = \(\frac{2m - m} {2m + m} g\) = a = \(\frac{g}{3}\)

Case (b):

FBD of mass m 

ma’ = T – mg 

ma’ = 2 mg – mg 

⇒ ma’ = mg 

a’ = g 

So in case (b) acceleration of m is more.

Corrrect answer is (b) \(\frac{m_2 F}{m_1 +m_2}\)

(b) Aristotle

Change in momentum can be achieved in two ways. 

They are: 

1. A large force acting for a short period of time and 

2. A smaller force acting for a longer period of time.

Due to inertia of motion.

True. The total momentum of a system of particles is always constant i.e. conserved. When no external force acts on it.

(c) always zero

Correct answer is (a) zero

Force of friction = 0·5 N per quintal 

f = 0·5 × 2000 = 1000 N 

m = 2000 quintals = 2000 × 100 kg

sin θ = 1/50, a = 2 m/s² 

In moving up an inclined plane, force required against gravity 

= mg sin θ = 39200 N 

And force required to produce acceleration = ma 

= 2000 × 100 × 2 = 40,0000 N 

Total force required = 1000 + 39,200 + 40,0000 

= 440200 N.

Suppose, a = acceleration produced if m and m are tied together, 

F = 100 N

 Let a₁ and a₂ be the acceleration produced in m₁ and m₂ respectively. 

∴ a₁ and a₂ = 20ms^-2 (given)

Again m₁ = \(\frac{F}{a_1}\) and  m₂ = \(\frac{F}{a_2}\)

⇒ m₁ = \(\frac{100}{10}\) =10 kg

and m₂ = \(\frac{100}{20}\) = 5 kg

∴ m₁ + m₂ = 10 + 5 = 15

so, a = \(\frac{F}{m_1 + m_2}\) = \(\frac{100}{15}\)= \(\frac{20}{3}\) = 6.67 ms²

Correct answer is (a) Galileo

As the friction between the types and road reduces on a rainy day.

By Newton’s second law, 

F = ΔP/t (Δ refers to change) 

ΔP = F × t 

J = ΔP 

F × t = ΔP

Impulse is also equal to the magnitude of change in momentum. Its unit is kg ms^-1 or N s.

When a force F acts on a body for a period of time t, then the product of force and time is known as ‘impulse’ represented by ‘J’ 

Impulse, J = F × t