Question

A driver parked his car on a steep hill and forgot to set the emergency brake. As a result, the car rolled down the hill and crashed into a parked truck. If the car was moving at 10 mph (4.5 m/s) when it hit the truck 7.0 seconds after it began to move, what was the car’s average acceleration while it rolled down the hill? Define the positive x direction to be down the hill.

Answer 1

Answer:0.642

Step-by-step explanation:

Given

initially car is at rest i.e u=0

When car hits the truck it's velocity is 4.5 m/s

it hits the truck after 7 sec

Now average acceleration of car is =
`(change\ in\ velocity)/(time\ taken)`

average acceleration of car =
`(\left ( final velocity\right )-\left ( initial velocity\right ))/(time)`

average acceleration of car=
`(\left ( 4.5\right )-\left ( 0\right ))/(7)`

average acceleration of car=
`0.642 m/s^(2)`

Taking Down hill as positive x axis

average acceleration of car=
`0.642\hat{i}`