Question

Table 2.5 shows how the velocity of a car changed during part of a journey along a main road. (a) Draw a velocity–time graph for the journey. (b) Write a brief description of the journey. (c) The car’s speed changed during two parts of the journey. Calculate its acceleration at these times. Table 2.5 Data for part of a car journey – see Question 6 Velocity (m/s) 16 20 24 24 24 21 18 Time (s) 0 10 20 40 60 70 80

Answer 1

a) The velocity-time graph:

b) The journey consists of acceleration from the start to 20 s, uniform motion at constant velocity between 20 and 60 s, and deceleration from 60 to 80 s.

c) The speed of uniform motion:

$$v=24\text{ m/s}.$$

The acceleration and deceleration (the magnitude is the same):

$$a=\Delta v/t=(24-16)/(20-0)=0.4\text{ m/s}^2.$$