Question

Question 35:
What is the momentum in kg.m/s of a 10 kg car travelling at (a) 5 m/s (b) 20 cm/s, and (c) 36 km/h ?

Lakhmir Singh Physics Class 9

Answer 1

Given , mass = 10 kg

1) When speed is 5 m/s then momentum

= mv = 10 × 5

= 50 kgm/s

2) Speed = 20 cm/s

First of all convert velocity in to m/s

which will be 20/100 = 0.2 m/s

Using momentum = mv = 10 × 0.2 kg m/s

= 2 kg m/s

3) Speed = 36 km/h = 10 m/s

momentum = 10 × 10

= 100 kg m/s

Answer 2

Given m=10 kg and v=5m/s
momentum = mv= 10 kg ×5m/s = 50kg m/s
If v = 20 cm/s = (20/100)m/s=(1/5)m/s,
momentum = mv =10 kg × (1/5) m/s = 2 kg m/s
And, if v = 36 km/h = 36×(5/18) m/s = 10m/s,
momentum = mv = 10 kg × 10 m/s = 100 kg m/s