Ablock is launched up an incline plane. after going up the plane, it slides back down to its starting position. the coefficient of friction between the block and the plane is 0.3. the speed of the block when it reaches the starting position on the trip down: a. is the same as the launching speed. b. is less than the launching speed. c. is more than the launching speed. d. cannot be compared to the launch speed with the information given.

b. is less than the launching speed.

Explanation:

According to the law of energy conservation, the total mechanical energy remain the same. In our case the block starts with some kinetic energy, this energy is then lost to friction force, which dissipates as heat energy to external environment. Therefore, its kinetic energy when coming back must be less than its kinetic energy at launch, and the same for its speed, as mass is unchanged.

conservation of mass

mass before something happens = mass afterwards