Forces & Newton’s Laws — A/L Physics

How do I practise Forces & Newton’s Laws?

1 question with a worked solution

1. A 0.20 kg rubber ball traveling horizontally at 15 m s⁻¹ strikes a vertical wall normally and rebounds horizontally with a speed of 10 m s⁻¹. If the duration of contact is 0.05 s, what is the average force exerted by the wall on the ball?
   1. A) 80 N
   2. B) 20 N
   3. C) 60 N
   4. D) 100 N
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   Correct answer: D) 100 N

   Taking the rebound direction as positive: initial velocity u = -15 m s⁻¹, final velocity v = +10 m s⁻¹. Impulse J = m(v - u) = 0.20 kg × (10 - (-15)) m s⁻¹ = 0.20 × 25 = 5.0 N s. Average force F = J / Δt = 5.0 N s / 0.05 s = 100 N.

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   Step 1: Calculate impulse J = m(v - u) = 0.20 × (10 - (-15)) = 5.0 N·s. Step 2: Calculate average force F = J / Δt = 5.0 / 0.05 = 100 N. Answer: 100 N.
   Modelled on: the A/L Physics examination pattern

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Where does Forces & Newton’s Laws fit in the syllabus?

Unit 2.2 · Year 1 · Term 1