Question

The catcher prepares to receive a pitch from the pitcher. As the ball reaches and makes contact with his glove, the catcher pulls his hand backward. This action reduces the impact of the ball on the catcher’s hand because:

A. The energy absorbed by his hand is reduced

B. The momentum of the pitch is reduced

C. The time of impact is increased

D. The time of impact is reduced

E. The force exerted on his hand remains the same

Answer 1

When pitch is released from the pitcher it is having a momentum. We know that an object possessing a certain amount of momentum can only be stopped when we apply force for a certain time. Suddenly stopping this object with some momentum will definitely have an impact on the catcher’s hand. You could recall the expression for impulse to find the reason behind the mentioned action of the catcher.

Formula used:

Impulse,

$F\centerdot t=m\Delta v$

Complete answer:

In the question, we are given the case of a catcher preparing to receive a pitch from a pitcher. The catcher is pulling his hands backward as the ball reaches and makes contact with his glove. We are asked to find the reason behind this action of the catcher and thus find how the impact of the ball is being reduced due to this action.

We know that it is difficult to stop anything that has momentum. If we were to stop an object that has momentum, then we will have to apply a force against its motion for a particular interval of time. So it is quite obvious that the more the momentum of the object is the harder it will be to stop it. While we apply force for a period of time, we are actually changing the object’s momentum.

Now let us explain this mathematically using Newton’s second law.

${{F}_{net}}=ma$

$\Rightarrow {{F}_{net}}=m\dfrac{\Delta v}{t}$

$\Rightarrow F\centerdot t=m\Delta v$

In physics, force ×time is called impulse and $m\Delta v$ is the change in momentum of the body.

$F\times t=m\left( {{v}_{2}}-{{v}_{1}} \right)$

As the catcher catches the pitch, the pitch going to rest that is the final velocity ${{v}_{2}}$ becomes zero. Therefore,

$F\times t=-m{{v}_{1}}$

As the catcher pulls his hands backwards the time of impact (t) is increased and thereby reducing the impact on his hands.

Therefore, the answer to the given question is option C.

Note: It is for the same reason that a fielder in cricket pulls his arm backward while catching the ball. Otherwise the impact caused by the ball will be too high for his hands and he may even get injured. While driving when you apply the brake for a given amount of time, you are actually changing the car’s momentum.