Question

The surface of the preceding problem is modified so that the coefficient of kinetic friction is decreased. The same horizontal force is applied to the crate, and after being pushed 8.0 m, its speed is 5.0 m/s. How much work is now done by the force of friction? Assume that the crate starts at rest.

(a) 200 J
(b) 150 J
(c) 100 J
(d) 50 J

Answer 1

The work done by the force of friction can be found by calculating the change in kinetic energy of the crate. Use the formulas for work and kinetic energy to solve for the desired quantity.

Step-by-step explanation:

To find the work done by the force of friction, we need to calculate the change in kinetic energy of the crate.

The work done by a force can be calculated using the formula work = force * distance * cos(theta), where theta is the angle between the force and the displacement.

In this case, the force of friction acts opposite to the direction of motion, so theta is 180 degrees.

We are given the distance pushed (8.0 m) and the final speed of the crate (5.0 m/s).

Using the formula kinetic energy = 0.5 * mass * velocity^2, we can calculate the initial kinetic energy (before being pushed) and the final kinetic energy (after being pushed).

Subtracting the final kinetic energy from the initial kinetic energy gives us the change in kinetic energy.

The work done by the force of friction is equal to the change in kinetic energy.