In order for an object to conserve it's total mechanical energy it is absolutely necessary that ?

Agenerator converts mechanical energy to electrical energy. when a coil placed between two magnets rotates, the magnetic lines of force are disturbed. this induces a current in the coil. the image below shows a generator. what could be done to make the lamp brighter? a. decrease the size of the magnets b. turn the coil slower c. change the polarity of the magnets d. turn the coil faster

Identical marbles are released from the same height on each of the following four frictionless ramps . compare the speed of the marbles at the end of each ramp. explain your reasoning

Aball tossed vertically upward from the ground next to a building passes the bottom of a window 1.8 s after being tossed and passes the top of the window 0.20 s later. the window is 2.0 m high from top to bottom. what was the ball's initial velocity? the unit vector j^ is directed upward. how far is the bottom of the window from the launch position? how high does the ball rise above the launch position?