IB Physics SL A.2.17 Impulse

Practise calculating impulse from force-time information or vector momentum change, retaining direction through rebounds and linking contact time to average resultant force.

Exam points

calculate impulse as the signed area under a force-time graph, including triangular or variable-force regions
find Δp = m(v - u) with a consistent positive direction, especially when an object rebounds
use average resultant force Δp/Δt and include other forces when the question requires a net force

[Maximum number: 2]

A student strikes a tennis ball that is initially at rest so that it leaves the racquet at a speed of $64 \mathrm{~m} \mathrm{~s}^{-1}$ . The ball has a mass of 0.058 kg and the contact between the ball and the racquet lasts for 25 ms .

Calculate the

average force exerted by the racquet on the ball.

$\begin{aligned} F=\frac{\Delta m v}{\Delta t} / m \frac{\Delta v}{\Delta t} / \frac{0.058 \times 64.0}{25 \times 10^{-3}} F=148 \text { «N» } \approx 150 \text { «N» } \end{aligned}$

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A.2.17—Impulse question 1