A2 Daily A Level Physics question
On a wet test track, a car drives a steady circular path of fixed radius. On a second run it keeps the same path but increases its speed by 50%. For the car’s acceleration directed towards the centre, what is the percentage change?
Answer
The correct answer is B.
Correct: B — increases by 125%. A The inward acceleration depends on the square of speed, not directly on speed, so a 50% speed increase does more than a 50% acceleration increase. B At fixed radius the inward acceleration is proportional to speed squared, so multiplying speed by 1.5 multiplies acceleration by (1.5)^2 = 2.25, i.e. a 125% increase over the original. C This confuses the final value being 225% of the original with the percentage increase; 2.25 times the original is a 125% increase, not 225%. D It cannot stay the same because changing speed on the same radius changes the required inward acceleration.