Kinetic energy, ke
4 marks · NormalA student drops a metal ball bearing (mass 0.15 kg) from rest at a height of 2.5 m above the ground. Ignore air resistance.
Calculate the gravitational potential energy of the ball bearing at the top.
State the value of kinetic energy just before the ball hits the ground.
Explain your reasoning.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 3.75 J
(b) 3.75 J
(c) All the initial GPE is transferred to KE as the ball falls (ignoring air resistance). · must show statement of conservation of energy, mention of GPE to KE transfer
Common mistakes: Confusing mass and weight; Not stating/understanding energy conservation
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correct substitution for GPE = mgh
A1 (a) · 1 mark · Correct value of GPE (3.75 J)
B1 (b) · 1 mark · States KE = GPE at ground (3.75 J) (follow-through)
B2 (c) · 1 mark · Correctly explains using conservation of energy
Worked solution
a)
b)
3.75 J
c)
Ignoring air resistance, all the gravitational potential energy is converted to kinetic energy as it falls.