Question

A body of mass $5kg$ undergoes a change in speed from $20m{s}^{-1}$to $0.20m{s}^{-1}$. The momentum :

• A. increases by $99kgm{s}^{-1}$
• B. decreases by $99kgm{s}^{-1}$
• C. increases by $101kgm{s}^{-1}$
• D. decreases by $101kgm{s}^{-1}$

Answer 1

The correct option is B

decreases by $99kgm{s}^{-1}$

Explanation for the correct option

(B): decreases by $99kgm{s}^{-1}$

Step 1: Given data

u = $20m{s}^{-1}$ , v = $0.20m{s}^{-1}$ , m = $5kg$

Step 2: Finding momentum

Formula:

Change in momentum Δp = m ( v- u )

where,

u = Initial speed of the body

v = Final speed of the body

Δp = Change in momentum

m = mass of the body

Now, put the following value in the formula

Δp = $5(0.20-20)$

= $-99kgm{s}^{-1}$

Hence when A body of mass $5kg$ undergoes a change in speed from $20m{s}^{-1}$to $0.20m{s}^{-1}$. The momentum of the body decreases by $99kgm{s}^{-1}$. Hence option (b) is correct.