# Bat Force and Human Lifting Capacity in Softball Pitching

• Mowgli
In summary, a 0.165kg softball pitched at 20.0m/s and hit back with the same speed and contact time of 9.90x10^-3 seconds exerts an average force of 666.7 N or 6.70x10^3 N on the ball. This force is greater than the force needed to lift a 70kg person, which is calculated to be 684.9 N or 6.80x10^2 N. Therefore, more force would be needed to lift the person.
Mowgli

## Homework Statement

A 0.165kg softball is pitched to you at 20.0m/s. You hit the ball back along the same path, and at the same speed. If the bat was in contact with the ball for 9.90x10^-3 seconds,

a.) what was the average force the bat exerted on the ball?

b.) Could this force lift a 70.0kg person?

## Homework Equations

I believe the equation to use is

mass/change in time x (final velocity + initial velocity)

## The Attempt at a Solution

a.)

(.165kg (20 + 20 m/s)) / 9.90 x 10^-3
= .165(40) / .0099
= 666.7 N
= 6.70 x 10^3 N

b.)

How do I factor in a 70kg person? Do I use 70(40)/.0099 ?

What force is required to lift a 70 kg person?

Look at your equation again. Force is equal to the change in momentum over time. Change in momentum = final - initial.

so I should have .165(20-20)/.0099 and get 16.7 N??

you're hitting the ball back, so the final momentum should be negative.

Can someone confirm this?

Mowgli said:
I believe the equation to use is

mass/change in time x (final velocity + initial velocity)
That equation should be: mass/change in time x (final velocity - initial velocity)

But as mizzy says, the sign of the velocity changes since you're hitting the ball in the opposite direction. So 20 - (-20) = 20 + 20.

(All we care about is the magnitude of the change, so it doesn't matter which direction we call negative.)

## The Attempt at a Solution

a.)

(.165kg (20 + 20 m/s)) / 9.90 x 10^-3
= .165(40) / .0099
= 666.7 N
= 6.70 x 10^3 N
That's fine, except for the last step. (You have the wrong exponent.)

Oooh, okay. Yes I noticed it should be ^2

Thank you.

To figure out b.)?? Can this be used to lift a 70kg person? Anyone?

mizzy said:
you're hitting the ball back, so the final momentum should be negative.

Can someone confirm this?
If the initial momentum was positive, then the final would be negative. (But all we really care about is the magnitude of the change.)

Mowgli said:
Oooh, okay. Yes I noticed it should be ^2
Make sure you understand the point that mizzy was making.

To figure out b.)?? Can this be used to lift a 70kg person? Anyone?
What force is required to lift a 70 kg person?

F= 70kg x 9.90x10^-3
= 70x.0099
= .693 N

.693 < 666.7 so less force is required to lift the person?

you multiplied mass by time??

or by speed? I'm not sure what to use.

70.0kg x 20.0 m/s
= 1400
= 1.4 X 10^3

I'm not too sure. But in your previous answer, mass x time doesn't give you F. Force is in Newtons (kgm/s^2)

The answer to my question--What force is required to lift a 70 kg person?--has nothing to do with momentum, speed, or time.

How much does the person weigh?

the person weighs 70kg

Mowgli said:
the person weighs 70kg
That's his mass, not his weight. How do you calculate the weight?

into lbs? multiply by 2.20

so 154 lbs

Mowgli said:
into lbs? multiply by 2.20

so 154 lbs
Better calculate the weight in Newtons so you can compare it to the force you calculated in part a.

oooh! so 154lb x 4.448N
= 684.9N
= 6.80x10^2
and
6.70x10^2 < 6.80x10^2
therefore more force would be needed to life the 70kg person

Mowgli said:
oooh! so 154lb x 4.448N
= 684.9N
= 6.80x10^2
and
6.70x10^2 < 6.80x10^2
therefore more force would be needed to life the 70kg person
That's the idea.

But the easy way to calculate the weight is by using W = mg, where g = 9.8 m/s^2.

Doc Al said:
That's his mass, not his weight. How do you calculate the weight?

weight = mass x accleration of gravity

got it :) thank you!

## 1. What is momentum?

Momentum is a measure of an object's motion. It is calculated by multiplying an object's mass by its velocity.

## 2. How is momentum conserved?

Momentum is conserved in a closed system, meaning that the total momentum before and after a collision or interaction remains the same. This is known as the law of conservation of momentum.

## 3. What is the difference between linear and angular momentum?

Linear momentum refers to the motion of an object in a straight line, while angular momentum refers to the motion of an object around an axis. Both types of momentum are conserved in a closed system.

## 4. How does momentum relate to Newton's laws of motion?

Newton's second law states that the force acting on an object is equal to its mass multiplied by its acceleration. This can also be written as the rate of change of momentum. Therefore, momentum is directly related to the forces acting on an object.

## 5. Can momentum be transferred between objects?

Yes, momentum can be transferred between objects in collisions or interactions. This transfer can be seen in sports such as billiards, where the momentum of the cue ball is transferred to the other balls upon impact.

Replies
2
Views
2K
Replies
3
Views
5K
Replies
2
Views
2K
Replies
6
Views
5K
Replies
2
Views
4K
Replies
3
Views
19K
Replies
14
Views
2K
Replies
6
Views
3K
Replies
2
Views
3K
Replies
8
Views
2K