IB Physics HL A 2 18 Impulse Momentum Change Questions

Practise analysing momentum change in rebounds, collision-force calculations, stopping-time safety and momentum transfer from ejected mass.

Exam points

Relate the applied external impulse to the change in momentum of the system, J = Δp.
Calculate momentum change, impulse or average force and interpret the system boundary and external-force assumptions using complete evidence.

[Maximum number: 3]

A toy rocket is made from a plastic bottle that contains some water.

Air is pumped into the vertical bottle until the pressure inside forces water and air out of the bottle. The bottle then travels vertically upwards.

Figure for Question IB Physics HL A 2 18 Impulse Momentum Change Questions question 1 — IB Physics HL

The air-water mixture is called the propellant.
The variation with time of the vertical velocity of the bottle is shown.

The bottle reaches its highest point at time $T_{1}$ on the graph and returns to the ground at time $T_{2}$ . The bottle then bounces. The motion of the bottle after the bounce is shown as a dashed line.

The bottle bounces when it returns to the ground.

The mass of the bottle is 27 g and it is in contact with the ground for 85 ms .

Determine the average force exerted by the ground on the bottle. Give your answer to an appropriate number of significant figures.

Attempt to use force = momentum change ÷ time $<=\frac{(4.5+10) \times 0.027}{85 \times 10^{-3}}=4.6 \gg$

Force $=\ll 4.6+0.3>4.9<\mathrm{N} \gg$

Any answer to 2 sf

Marking guidance:

Accept ± 0.5 velocity values from graph

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IB Physics HL A 2 18 Impulse Momentum Change Questions question 1