Trying to pass physics be like:

A ball is dropped from rest and falls to the floor. The initial gravitational potential energy of the ball-Earth-floor system is 10 J. The ball then bounces back up to a height where the gravitational potential energy is 7 J. What was the mechanical energy of the ball-Earth-floor system the instant the ball left the floor?

• 4J

• 6J

• 7J

• 10J

A block of mass M is released from rest at point 1, as shown in the figure. The block slides without frictional forces along the circular arc but encounters frictional forces as soon as it reaches the horizontal portion of the track at point 2. The block travels a distance D along the horizontal track before coming to rest at point 3. Consider the block-Earth system. In terms of the mechanical energy of the system, which of the following claims is correct, and why?

• The system is closed because a net force is exerted on the block.

• The system is open because a net force is exerted on the block.

• The system is open because the velocity is zero at points 1 and 3.

• The system is closed because the velocity is zero at points 1 and 3.

An inclined track is secured to a table. The height of the highest point of the above the tabletop is h1. The height from the tabletop to the floor is h2. A block of as M is released from rest and slides down the track such that all the frictional forces are considered negligible. The block leaves the track horizontally and strikes the ground at a distance D. Which of the following statements is correct about the scenario? Select two answers.

• the total mechanical energy of the system containing only the block increases from the moment of release to the moment it hits the ground.

• the total mechanical energy of the system containing only the black remains constant

• the total mechanical energy of the block-earth system remains constant

• the total mechanical energy of the block-earth system increases from the moment of release to the moment it hits the ground.