A car travels 30km at a uniform speed 30km/h and the next 30km at a un

1.	A car travels 30km at a uniform speed 30km/h and the next 30km at a uniform speed of 60km/h. The average speed of the car is : (a) 45km/h (b) 50km/h (c) 40km/h (d) None of the three.
Answer» A car travels 30km at a UNIFORM speed 30km/hr and the next 30km at a uniform speed of 60km/hr. We have to find the AVERAGE speed of the car. Now, Average speed is defined as the ratio of total DISTANCE covered with respect to total time TAKEN. Whereas average velocity is defined as the ratio of total displacement with respect to total time taken. As the distance covered by the car is same i.e. 30 km. So, the total distance covered by the car is 60 km (30+30). Also, Time = Distance/Speed t1 = 30/30 hr and t2 = 30/60 hr Total time taken = t1 + t2 = 1 + 1/2 = 3/2 hr Average speed = (Total distance covered)/(Total time taken) = 60/(3/2) = 40 THEREFORE, the average speed of the car is 40 km/hr. Option (c) 40 km/hr

A car travels 30km at a uniform speed 30km/h and the next 30km at a uniform speed of 60km/h. The average speed of the car is : (a) 45km/h (b) 50km/h (c) 40km/h (d) None of the three.

Answer»

A car travels 30km at a UNIFORM speed 30km/hr and the next 30km at a uniform speed of 60km/hr.

We have to find the AVERAGE speed of the car.

Now,

Average speed is defined as the ratio of total DISTANCE covered with respect to total time TAKEN. Whereas average velocity is defined as the ratio of total displacement with respect to total time taken.

As the distance covered by the car is same i.e. 30 km. So, the total distance covered by the car is 60 km (30+30).

Also,

Time = Distance/Speed

t1 = 30/30 hr and t2 = 30/60 hr

Total time taken = t1 + t2

= 1 + 1/2

= 3/2 hr

Average speed = (Total distance covered)/(Total time taken)

= 60/(3/2)

= 40

THEREFORE, the average speed of the car is 40 km/hr.

Option (c) 40 km/hr

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