Question

A cricket ball weighing 100 g and moving with a speed of 20 m s –1 strikes a bat and remains in contact with it for 0.1 s. The average force exerted by the ball on the bat is

Answer 1

Answer: 20 N

Explanation:

From Newton's second law of motion, we know that

Force = rate of change of momentum.

The mass of the ball is, m = 100 g = 0.1 kg

velocity of ball, v = 20 m/s

Time of contact, t = 0.1 s

The momentum of the ball at the time of contact = mv

Average force force exerted by the ball on the bat:

$F=\frac{mv}{t} = \frac{0.1 kg\times 20 m/s}{0.1 s}=20 N$

Thus, the average force exerted by the ball on the bat is 20 N.

Answer 2

weight of cricket ball, m = 100g = 0.1 kg
speed of cricket ball, v = 20 m/s
so, initial linear momentum of ball, $P_i$ = mv = 0.1 × 20 = 2 kgm/s

a/c to question, after striking a bat , ball remains in contact with it for 0.1 sec.
so, final linear momentum , $P_f$ = 0

now, change in linear momentum = 2 - 0 = 2kgm/s

we know, force = change in momentum/time
= 2/0.1 = 20 N