Question

A car traveling at 25 m/s starts to decelerate steadily. It comes to a complete stop in 6 seconds. What is its acceleration? Your Answer: Question 2 options: Answer units

Answer 1

Since the acceleration of the car is constant, the car is moving by uniformly accelerated motion, and the velocity of the car at time t can be written as

`v(t) = v_0 + at`
where
`v_0 = 25 m/s` is the initial velocity of the car
a is the acceleration
t is the time
At time
`t = 6 s`, the velocity of the car is zero:
`v(t)=0`, so we can re-arrange the previous formula to get the acceleration of the car

`a=- (v_0)/(t)=- (25 m/s)/(6 m/s)=-4.17 m/s^2`
and the negative sign means the direction of the acceleration is against the direction of motion of the car (in fact, the car is decelerating).