Question

A block is released from rest at point A, and it slides down a frictionless curved slope to point B. It continues to slide, with friction, along a horizontal section until it comes to rest at point C. Point A is a height h above point B. A time t elapses as the block travels the horizontal distance x from point B to point C.

a. The work done by friction is zero. b. The work done by friction is positive. c. The work done by friction is negative. d. The work done by friction depends on the coefficient of friction.

Answer 1

The work done by friction is negative because the frictional force acts opposite to the displacement of the block, causing a loss in kinetic energy as the block slides from point B to point C.

Step-by-step explanation:

In physics, when a block slides along a surface with friction, the work done by the frictional force is considered negative. This is because the frictional force acts in the opposite direction to the displacement of the block. Thus, when a block slides from point B to point C, the frictional force is doing work on the block in the opposite direction to its motion, leading to a loss in the block’s kinetic energy.

In the case of the block being released from a height h at point A and sliding down to point B without friction and then continuing to point C with friction, the work done by friction on the horizontal part of the path (from B to C) is negative. This is because the kinetic energy of the block is being converted into thermal energy due to friction, which opposes the motion until the block comes to a rest.

Therefore, the correct answer to the question is c. The work done by friction is negative.