What is the physical reason for a cricket fielder pulling his hands backwards while catching a fast-moving ball?

Correct Option

The correct option is

To increase the time of impact, thereby reducing the force exerted by the ball.

Explanation

The physical principle governing this action is Newton's Second Law of Motion, specifically the relationship between force, momentum, and time. The law states that the force applied is equal to the rate of change of momentum ($F = \frac{\Delta p}{\Delta t}$).

Detailed Analysis

When a fielder catches a fast-moving cricket ball, the ball possesses a significant amount of momentum ($p = mv$). To complete the catch, the fielder must bring the ball to rest, reducing its momentum to zero.

• Change in Momentum ($\Delta p$): The total change in momentum required to stop the ball is constant, determined by the ball's mass and initial velocity.
• Role of Time ($\Delta t$): By pulling the hands backward along with the line of the ball's motion, the fielder increases the time interval ($\Delta t$) during which the ball's velocity is reduced to zero.
• Impact on Force ($F$): Since Force is inversely proportional to time ($F \propto \frac{1}{\Delta t}$) for a constant change in momentum, increasing the time of impact results in a corresponding decrease in the average force exerted by the ball on the hands.

Option Analysis:

• To increase the rate of change of momentum. is incorrect: Increasing the rate of change of momentum is equivalent to increasing the force, which would cause injury.
• To reduce the time of impact, thereby increasing the force. is incorrect: Reducing the time of impact would drastically increase the retarding force, leading to a harder impact on the hands.
• To increase the time of impact, thereby reducing the force exerted by the ball. is correct: Extending the time of impact reduces the impulsive force, making the catch safer and easier.
• To ensure the ball does not slip out of the hands due to friction. is incorrect: While friction aids in gripping the ball, the backward motion is a dynamic adjustment to manage impact force, not to manipulate friction.

Key Takeaway

Impulse-Momentum Theorem: To minimize the impact force during a collision (such as catching a ball), one must maximize the time duration over which the momentum changes.