IMAT 2019 Q53 [Car Acceleration]

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1

A car, which is initially stationary, accelerates for 5.0 seconds at 4.0 m / s^2 along a straight road. It then continues in the same direction for 20 seconds at a constant speed.

What is the maximum speed of the car, and what is the distance travelled by the car in the final 20 seconds of its motion?

A. maximum speed = 24 m / s; distance = 480 m
B. maximum speed = 20 m / s; distance = 400 m
C. maximum speed = 9.0 m / s; distance = 200 m
D. maximum speed = 9.0 m / s; distance = 180 m
E. maximum speed = 20 m / s; distance = 80 m

2

The maximum speed of the car must have been the speed it accelerates at, using quick calculations we can see that if the car accelerated 4 m for every second, then for 5 seconds it covered 20m. This makes for our maximum speed of 20m/s.

Using speed=distance/time, we can see that if we travel at this maximum of 20m/s speed for 20 seconds- we can cover 400m of distance.

Our answer is therefore B.

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