IB Physics SL A.2.1 Newton’s Three Laws of Motion

Practise drawing force explanations and applying Newton’s laws to equilibrium, acceleration, collisions and motion on slopes.

Exam points

Apply Newton’s laws to free-body diagrams, equilibrium and acceleration.
Use action-reaction pairs to explain collisions, lift, propulsion and contact forces.

[Maximum number: 4]

(a)

B3. This question is in two parts. Part 1 is about a collision. Part 2 is about electric current and resistance.
Part 1 A collision
Two identical blocks of mass 0.17 kg and length 0.050 m are travelling towards each other along a straight line through their centres as shown below. Assume that the surface is frictionless.

The initial distance between the centres of the blocks is 0.900 m and both blocks are moving at a speed of $0.18 \mathrm{~m} \mathrm{~s}^{-1}$ relative to the surface.

[ 4 ]

(i)

State Newton's third law of motion.

[ 1 ]

(ii)

During the collision of the blocks, the magnitude of the force that block A exerts on block B is $F_{\mathrm{AB}}$ and the magnitude of the force that block B exerts on block A is $F_{\mathrm{BA}}$ . On the diagram below, draw labelled arrows to represent the magnitude and direction of the forces $F_{\mathrm{AB}}$ and $F_{\mathrm{BA}}$ .

[ 3 ]

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A.2.1—Newton’s three laws of motion question 1

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