Question

A car starts from rest and attains a velocity of 40m/s in 20s. It maintains this velocity for 30s, and then comes to rest in 25s. What is the acceleration of the car?

Answer 1

To find the acceleration of the car, we can use the formula:

acceleration (a) = (final velocity (v) - initial velocity (u)) / time (t)

1. From rest to attaining a velocity of 40 m/s in 20 seconds: Initial velocity (u) = 0 m/s Final velocity (v) = 40 m/s Time (t) = 20 s

acceleration (a1) = (40 m/s - 0 m/s) / 20 s acceleration (a1) = 40 m/s / 20 s acceleration (a1) = 2 m/s²

2. Maintaining a velocity of 40 m/s for 30 seconds: In this case, the velocity remains constant, so the acceleration is 0 m/s².

3. Coming to rest from a velocity of 40 m/s in 25 seconds: Initial velocity (u) = 40 m/s Final velocity (v) = 0 m/s Time (t) = 25 s

acceleration (a2) = (0 m/s - 40 m/s) / 25 s acceleration (a2) = -40 m/s / 25 s acceleration (a2) = -1.6 m/s²

Note that the negative sign indicates deceleration (opposite direction to the initial motion) in this case.

Therefore, the acceleration of the car during different phases is as follows:

1. Acceleration from rest to 40 m/s in 20 s: 2 m/s²
2. Maintaining a velocity of 40 m/s: 0 m/s²
3. Deceleration from 40 m/s to rest in 25 s: -1.6 m/s²