Describe the motion shown in the velocity–time graphs of Fig. 2.20.
(i)
30 40
20
10 0
(ii) AB C FIG. 2.21 H 0
6 8
4
2 0
(iii)
12 16
8
4 0
FIG 2.20 10 20 Time (s) 30 40
17. A man is running at 5 m s–1 in order to overtake a car that is 5 m in front of him. At the same instant, the car accelerates away with a constant acceleration of 1.3 m s–2.
(i) How long does it take for the man to catch the car?
(ii) How long does it take before the car catches up with the man again after he has passed it?
18. Two cars 1.2 km apart are driving towards each other. One car is travelling at 50 m s–1 and the other car at 70 m s–1. How far away are they from each starting point when they meet?
0 15 30 Time (s) 45 60
19. Two trains are on a collision course 4 km apart, each travelling at 40 m s–1.
(i) If both trains begin to slow at the same rate and time, what must their acceleration be to just avoid collision?
(ii)
If, however, only one train slows at this rate, how far will this train go before colliding with the other?
D
16. The ticker tape of Fig. 2.21 was attached to a 50 Hz ticker timer and the following distances were measured: |AB| = 25 cm, |BC| = 20 cm, |CD| = 10 cm. Determine the acceleration of the body attached to the tape.
