A 6.0-kg block slides along a horizontal surface. If µk = 0.20 for the block and surface, at what rate is the friction force changing the mechanical energy of the block at an instant when its speed is 4.0 m/s?

Question

Quizplus · Accepted Answer

The frictional force is given by $ f_k = \mu_k \cdot m \cdot g $. The rate at which friction changes the mechanical energy is the power, $ P = f_k \cdot v $. Substituting the values, $ f_k = 0.20 \cdot 6.0 \cdot 9.8 = 11.76 \, \text{N} $. Therefore, $ P = 11.76 \cdot 4.0 = 47.04 \, \text{W} $, which is approximately −47 W, indicating energy is being lost.

A 60-Kg Block Slides Along a Horizontal Surface