Give reason:
a)Why a cricket player lowers his hand back while catching the
ball?
b)Why the gun recoils?
c) When the car takes a bend or curve, if not for seat belts, we
would get thrown away from the car. Why?
Answers
Answer:
a) While catching a ball, a cricket player lowers his hands, because by doing so, he increases the time of catch. That is, the person increases the time to bring about a given change in momentum, and hence rate of change of momentum decreases. Thus, a small force is exerted by ball on the hands.
b) When a bullet is fired from a gun, the gun exerts a force on the bullet in the forward direction. This is force is called as the action force. The bullet also exerts an equal and opposite force on the gun in the backward direction. Therefore a gun recoils when a bullet is fired from it.
C) It may not seem like much, but driving even a few kilometres per hour above the speed limit greatly increases the risk of an accident.
Answer:
a)Why a cricket player lowers his hand back while catching the
ball?
while catching a fast moving cricket ball , a fielder in the ground gradually pulls his hand backwards with the moving ball, In doing so, the fielder increases the time during which the high velocity of the moving ball descrease to zero. thus, the accleration of the ball is descreased and therefore the impact of catching the fast moving ball is also reduced.
A cricket player moves his hands backwards on catching a fast cricket ball to prevent injury to the hands.
Reason:
--->A fast moving cricket ball has a larger momentum.The momentum of the ball has to be reduced to zero in order to catch .
---->When cricket player moves his hands back , the time taken to reduce the momentum of the ball to zero is increased.
----> Due to more time taken to stop the ball, the rate of change of momentum of ball is reduced and hence a small force is exerted on the hands of players. So, the hands of player do not get hurt.
--->If the cricket player stops the fast moving ball suddenly, then large momentum of the ball will be reduced to zero in a very short time , due to which the rate of change of momentum of ball will very large which will exert a large impact force on player's hand causing the injury to his hands.
Conclusion:
To prevent injury to his hands, always a cricket player moves his hands backwards on catching a fast cricket ball
b)Why the gun recoils?
When a bullet is fired from a gun, the gun exerts a force on the bullet in the forward direction. This is force is called as the action force. The bullet also exerts an equal and opposite force on the gun in the backward direction. Therefore a gun recoils when a bullet is fired from it.
c) When the car takes a bend or curve, if not for seat belts, we
would get thrown away from the car. Why?
Inertia is the reason that people in cars need to wear seat belts. A
moving car has inertia, and so do the riders inside it. When the driver
applies the brakes, an unbalanced force is applied to the car. Normally,
the bottom of the seat applies an unbalanced force—friction—which
slows the riders down as the car slows. If the driver stops the car suddenly, however, this force is not exerted over enough time to stop the
motion of the riders. Instead, the riders continue moving forward with
most of their original speed because of their inertia.