Question 5
MotionA force F is required to keep a 5 kg mass moving round a cycle of radius 3.5 m at a speed of 7 ms−1. What is the speed, if the force is tripled?
- A.4.0 ms−1
- B.6.6 ms−1
- C.12.1 ms−1
- D.21.0 ms−1
Show the answer and explanation
Answer: C (12.1 ms−1)
Explanation
F = mv2/r, so v2 ∝ F at fixed m and r. Tripling F gives v = 7√3 ≈ 12.1 m s−1.