9702_s22_qp_11 Question 5

The curved line PQR is the velocity–time graph for a car starting from rest. 

What is the average acceleration of the car over the first 5 s? 

A the area below the curve PQ 

B the area of the triangle PQS 

C the gradient of the straight line PQ 

D the gradient of the tangent at Q 

ANSWER: C

The Physics Behind

• Options A and B give distance.
• Option D tells the instantaneous acceleration.
• Average acceleration is the gradient of the line PQ. This means that the instantaneous acceleration varies with time from 0 to 5 s, that is from a lower value changing at constant rate to a higher value. The gradient of line PQ gives the average of these acceleration values within this time interval.