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Chapter 4: Q7. (page 101)

What average force is required to stop a 950-kg car in 8.0 s if the car is traveling at 95 km/h?

Short Answer

Expert verified

The average force on the car is 3135 N.

Step by step solution

01

Step 1. Given data and assumption

During the motion, the car has a constant acceleration.The force on the vehicle is equal to the product of the mass and acceleration.

Given data:

The mass of the car is m=950kg.

The time to move the car is t=8.0s.

The initial speed of the car is

vi=95kmh=26.39ms

The final speed of the car is vf=0as the car stops at the end.

Assumption:

Let a be the acceleration of the car.

02

Step 2. Calculation of the average force

The acceleration of the car is

a=vf-vit=0-26.39ms8.0s=-3.30ms2

Therefore, from Newton’s second law, you get that the average force on the car is

F=ma=950kg×-3.30ms2=-3135N

(Negative value of the average force means that the average force is against the direction of the initial velocity.)

Hence, the average force on the car is 3135 N.

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