Q#42 (Past Exam Paper – November 2019 Paper 13 Q17)
The maximum useful output power of a car travelling on a horizontal road is P. The total resistive force acting on the car is kv2, where v is the speed of the car and k is a constant.
Which equation is correct when the car is travelling at maximum speed?
A v3 = P / k B v2 = P / k C v = (P/k)2 D v = (P/k)3
Solution:
Answer: A.
Power = P
Resistive force F = kv2
For a body moving with constant speed,
Power P = Force × velocity
P = F × v
P = (kv2) × v
P = kv3
Make v the subject of formula,
v3 = P / k
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