Question

A cricket ball of mass 150 gm is moving with velocity 12 m/s and is hit by a bat so that ball is turned back with 20 m/s. The force acts for 0.01s.The average force exerted by the bat on the ball is-
a)400 N b) 450 N c) 485 N d) 480 N

Answer 1

Question

A cricket ball of mass $150\mathrm{g}$ is moving with velocity $12\mathrm{m/s}$ and is hit by a bat so that ball is turned back with $20\mathrm{m/s}$. The force acts for 0.01 s. The average force exerted by the bat on the ball is

a) 400 N

b) 450 N

c) 485 N

d) 480 N

Solution

$$m = 150\mathrm{g} = 0.15\mathrm{kg}; \quad |v_i| = 12\mathrm{m/s}; \quad |v_f| = 20\mathrm{m/s}; \quad \Delta t = 0.01\mathrm{s}.$$

The second Newton's Law:

$$\vec{F} = m \vec{a};$$ $$\vec{F} = m \frac{\overrightarrow{\Delta v}}{\Delta t} = m \frac{\overrightarrow{v_f} - \overrightarrow{v_i}}{\Delta t}; \quad F = m \frac{|v_f| - (-|v_i|)}{\Delta t} = m \frac{|v_f| + |v_i|}{\Delta t} = 480\mathrm{N}$$

Answer: d) $F = 480\mathrm{N}$.

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