Question

An 8000-N car is traveling at 12 m/s along a horizontal road. When the brakes are applied, the car skids (slides) to a stop in 4.0 s. Find the work done on the car.

Answer 1

Answer:

192000 J or 192 kJ

Explanation:

Work done = Force × distance moved along the direction of force.

From the question,

W = F×d............... Equation 1

Where W = work done by the car, F = Force of the car, d = distance move by the car along the direction of the force.

We can calculate for d using the equation of motion

d = (v+u)t/2..................... Equation 2

Where v = Final velocity of the car, u = Initial velocity of the car, t = time.

Given: u = 12 m/s, v = 0 m/s(skids to a stop), t = 4.0 s

Substitute into equation 2

d = (12+0)4/2

d = 24 m.

Also given: F = 8000 N

Substitute into equation 1

W = 8000×24

W = 192000 J

W = 192 kJ.