Fig. 1 shows a student releasing a steel ball from a platform above a tray of sand. The ball has a mass of 0.50 kg and is released from rest. As it falls, i...
Question 1 Report
Fig. 1 shows a student releasing a steel ball from a platform above a tray of sand. The ball has a mass of 0.50 kg and is released from rest. As it falls, its gravitational potential energy changes. The student notices that the sand becomes slightly warmer after several drops.
(a) State the main energy store of the ball when it is held on the platform. [1]
(b) Describe the energy transfer that occurs while the ball is falling. [2]
(c) State one reason why not all of the energy transferred becomes kinetic energy of the ball. [1]
Answer Details
(a) The ball has a gravitational potential energy store when held above the ground. Its energy is due to its position in Earth’s gravitational field. [1]
(b) As the ball falls, energy is transferred from its gravitational potential energy store to its kinetic energy store. The ball speeds up, so its kinetic energy increases. [2]
(c) Not all of this transfer becomes kinetic energy because air resistance transfers some energy by heating to the thermal energy store of the air. [1]
Exam point: Energy is conserved, but it may be dissipated into thermal stores rather than all becoming useful kinetic energy.
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