FIGURE 8-8
-An object of mass 4 kg starts at rest from the top of a rough inclined plane of height 10 m as shown in Figure 8-8. If the speed of the object at the bottom of the inclined plane is 10 m/s, how much work is done by the force of friction? Use g = 10 m/s².

Question

FIGURE 8-8 FIGURE 8-8 -An object of mass 4 kg starts at rest from the top of a rough inclined plane of height 10 m as shown in Figure 8-8. If the speed of the object at the bottom of the inclined plane is 10 m/s, how much work is done by the force of friction? Use g = 10 m/s<sup>2</sup>. A) -100 J B) 100 J C) 0 D) -200 J E) 200 J

FIGURE 8-8 -An object of mass 4 kg starts at rest from the top of a rough inclined plane of height 10 m as shown in Figure 8-8. If the speed of the object at the bottom of the inclined plane is 10 m/s, how much work is done by the force of friction? Use g = 10 m/s<sup>2</sup>. A) -100 J B) 100 J C) 0 D) -200 J E) 200 J

-An object of mass 4 kg starts at rest from the top of a rough inclined plane of height 10 m as shown in Figure 8-8. If the speed of the object at the bottom of the inclined plane is 10 m/s, how much work is done by the force of friction? Use g = 10 m/s².

Quizplus · Accepted Answer

Using conservation of energy, we can find the gravitational potential energy at the top of the inclined plane: 
PE = mgh = (4 kg)(10 m/s^2)(10 m) = 400 J

Using conservation of energy, we can find the kinetic energy at the bottom of the inclined plane: 
KE = (1/2)mv^2 = (1/2)(4 kg)(10 m/s)^2 = 200 J

The work done by the force of friction is equal to the loss in mechanical energy: 
Work of friction = PE - KE = 400 J - 200 J = -200 J

Since the work of friction is negative (opposite in direction to the displacement of the object), the answer is D, -200 J.

FIGURE 8-8 -An Object of Mass 4 Kg Starts at Rest from at Rest