What are two factors that determine the thermal energy of a substance

When you drop a pebble from height a it reaches the ground with speed v if there is no air resistance. from what height should you drop it so it will reach the ground with three times the speed? (a) 9m (b) 3m (c) 6m (d) 18m

The free body diagram shows a box being pulled to the left up a 25-degree incline. the magnitude of the normal force is

Ryan is examining the energy of the particles in a bar of gold. what is ryan most likely studying?