Question

If a car decreases in speed to a stop from an initial speed of 21 m/s in a period of 3 s, what is the average acceleration of the car? Show all work.

Answer 1

-7m/s^2

Step-by-step explanation:

Observe that car will have deceleration because the speed is decreasing

a= v-u/t where v is the final velocity and "u" is the initial velocity

a= 0-21/3 v will be 0 because car is coming to a stop hence no speed

a= -21/3

a= -7m/s^2

Answer 2

Step-by-step explanation:

To find the average acceleration of the car, we need to use the formula:

average acceleration = (final velocity - initial velocity) / time

In this case, the initial velocity is 21 m/s and the final velocity is 0 m/s, so the average acceleration is:

average acceleration = (0 m/s - 21 m/s) / 3 s = -7 m/s^2

The negative sign indicates that the acceleration is in the opposite direction of the initial velocity, which makes sense because the car is slowing down.