AIR RESISTANCE AND TERMINAL VELOCITY
4 marks · NormalA stone is dropped from rest from a tall building and falls straight down through air.
Draw and label all the forces acting on the stone just after it is released.
Describe how the forces acting on the stone change as it falls and approaches terminal velocity.
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) — · must show Downward arrow labelled 'weight' or 'gravity', Upward arrow labelled 'air resistance' (smaller than weight)
(b) As the stone falls, air resistance increases while weight stays the same. Eventually, air resistance equals weight and the stone reaches terminal velocity. · must show Air resistance increases, Weight stays constant, Terminal velocity reached when forces are balanced
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Downward arrow labelled 'weight' or 'gravity'.
B2 (a) · 1 mark · Upward arrow labelled 'air resistance', smaller than weight.
B3 (b) · 1 mark · Describes air resistance increasing while weight stays constant.
B4 (b) · 1 mark · Explains terminal velocity is reached when air resistance equals weight.
Worked solution
a) The diagram should show two arrows on the stone: a longer downward arrow labelled 'weight', and a shorter upward arrow labelled 'air resistance'.
b) As the stone falls, it accelerates and its speed increases, so air resistance increases. The weight stays the same throughout. When air resistance becomes equal to weight, there is no net force, so the stone falls at constant terminal velocity.