IB Physics SL A.2.25 Direction Change in Circular Motion

Practise explaining why constant-speed circular motion is accelerated motion and identifying the inward resultant force needed to continuously change the velocity direction.

Exam points

state that velocity changes because its direction changes even when the speed remains constant
identify the inward resultant force that supplies centripetal acceleration towards the centre
explain an apparent outward throw through inertia when the upper body lacks sufficient inward force

[Maximum number: 4]

This question is in two parts. Part 1 is about two children on a merry-go-round. Part 2 is about electric circuits.

Part 1 Two children on a merry-go-round
Aibhe and Euan are sitting on opposite sides of a merry-go-round, which is rotating at constant speed around a fixed centre. The diagram below shows the view from above.

Figure for Question A.2.25—Direction change in circular motion question 1 — IB Physics SL

Aibhe is moving at speed $1.0 \mathrm{~ms}^{-1}$ relative to the ground.

(a)

Outline why Aibhe is accelerating even though she is moving at constant speed.

[ 2 ]

(b)

The diagram below shows a side view of Aibhe and Euan on the merry-go-round.

Explain why Aibhe feels as if her upper body is being "thrown outwards", away from the centre of the merry-go-round.

[ 2 ]

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A.2.25—Direction change in circular motion question 1

Question (a)

Question (b)