IB Physics SL A 2 7 Frictional Force Questions

Practise applying static and dynamic friction to blocks, slopes, circular motion and accelerating systems.

Exam points

Identify friction as a force parallel to the contact surface and distinguish static friction, Ff ≤ μsFN, from dynamic friction, Ff = μdFN.
Calculate limiting or kinetic friction and use its direction and magnitude in complete force-balance or motion evidence.

[Maximum number: 3]

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 .

The student models the bounce of the tennis ball to predict the angle $\theta$ at which the ball leaves a surface of clay and a surface of grass.

Figure for Question IB Physics SL A 2 7 Frictional Force Questions question 1 — IB Physics SL

The model assumes
- during contact with the surface the ball slides.
- the sliding time is the same for both surfaces.
- the sliding frictional force is greater for clay than grass.
- the normal reaction force is the same for both surfaces.
Predict for the student's model, without calculation, whether $\theta$ is greater for a clay surface or for a grass surface.

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IB Physics SL A 2 7 Frictional Force Questions question 1