Question

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?

Answer 1

(a) 5 m/s
We know that:
Momentum = mass × velocity
= m × v
Here, mass, m = 10 kg
velocity, v = 5 m/s
Putting these values in the above formula, we get:
Momentum = 10 × 5 kg.m/s
= 50 kg.m/s

(b) 20 cm/s
We know that:
Momentum = mass × velocity
= m × v
Here, mass, m = 10 kg
velocity, v = 20 cm/s
v = 0.2 m/s
Putting these values in the above formula, we get:
Momentum = (10)(0.2) kg.m/s
= 2 kg.m/s

(c) 36 km/h
We know that:
Momentum = mass × velocity
= m × v
Here, mass, m = 10 kg
velocity, v = 36 km/h
$$\begin{gathered} =36\times \frac{1000}{3600} \\ =36\times \frac{10\cancel{00}}{36\cancel{00}} \\ =\cancel{36}\times \frac{10}{\cancel{36}} \\ =10\mathrm{m}/\mathrm{s} \end{gathered}$$
Putting these values in the above formula, we get:
Momentum = 10 × 10 kg.m/s = 100 kg.m/s