Contradiction in Force*Time Applications: Where Am I Wrong?

  • Thread starter E8
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In summary, the two applications of contact time, one for hitting a ball and the other for breaking objects or people, may seem contradictory at first. However, they are based on the principle of force multiplied by time equals change in momentum. When hitting a ball, the goal is to maximize the total momentum transferred to the ball, so maintaining contact for as long as possible is beneficial. But when trying to break something, the focus is on maximizing force or specific momentum, meaning a shorter contact time with a higher force is more effective. This seeming paradox can be explained by the differences in elastic and inelastic collisions and the properties of rigid and non-rigid bodies.
  • #1
E8
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I'm confused w/ whether or not I want to or not want to maintain contact w/ something when I strike it to get the most affect. For example they say when you're hitting a baseball or a golf ball to maintain contact as long as possible (the 'follow through') to drive it as far as you can. However, when trying to karate chop boards in half or trying to knock-out somebody w/ a punch they say to minimize the contact time. Both are based on Force*time=change in momentum.

It seems like the 2 contact time applications are contradictory where am I going wrong?
 
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  • #2
Greetings E8 !

When you strike a ball you need to maximize
the total momentum on it.
Momentum is p = m * v , where m is mass and
v is velocity. The total momentum on the ball
is the sum of all the momentum transferred to it
during the time of the interaction and so as
long as your club still has some forward momentum
left it's better to transfer as much of it as
possible to the ball.

When you try to break something you need to maximize
your force or specific momentum. That is, you need a peak
in momentum at some point thus resulting in a greater
force F = m * a = m * v / t = p / t at that specific
moment, to break whatever it is you're trying to break.

Live long and prosper.
 
  • #3
Originally posted by E8
I'm confused w/ whether or not I want to or not want to maintain contact w/ something when I strike it to get the most affect. For example they say when you're hitting a baseball or a golf ball to maintain contact as long as possible (the 'follow through') to drive it as far as you can. However, when trying to karate chop boards in half or trying to knock-out somebody w/ a punch they say to minimize the contact time. Both are based on Force*time=change in momentum.

It seems like the 2 contact time applications are contradictory where am I going wrong?

If what you're hitting is a house with a head and has a name like "Vini" - remain in contact for as short a time as possible. Then turn and run as fast as possible. :-)

Pmb
 
  • #4


Originally posted by drag
When you try to break something you need to maximize
your force or specific momentum. That is, you need a peak
in momentum at some point thus resulting in a greater
force F = m * a = m * v / t = p / t at that specific
moment, to break whatever it is you're trying to break.
There is a seeming paradox here: For example, though the tensile strength of steel is far higher than aluminum, steel requires less energy to break in an impact. There is a piece of equipment called a Charpy tester where you put small blocks of a given material into a device and swing an axe-like pendulum at them. When the pendulum breaks the block, it swings up to a specific height. The difference between the starting height and the new height is the kinetic energy required to break it - its the impact strength. Most steel is relatively brittle. When the pendulum hits it, it bends very little, concentrating the energy into a short, fast, hard force that easily snaps the block. Aluminum on the other hand is more ductile (softer). When the pendulum hits it, the energy is obsorbed when the aluminum bends. Because of this it takes many times as much energy to break an aluminum block in an impact than it does steel. Its acually a neat lab in materials science.
 
  • #5


Originally posted by russ_watters
When the pendulum hits it, it bends very little, concentrating the energy into a short, fast, hard force that easily snaps the block. Aluminum on the other hand is more ductile (softer). When the pendulum hits it, the energy is obsorbed when the aluminum bends. Because of this it takes many times as much energy to break an aluminum block in an impact than it does steel. Its acually a neat lab in materials science.
I think that has to do more with elastic/non-elestic
collisions and rigid/non-rigid bodies.
 
  • #6
When you hit a ball, you want to add as much momentum to it as possible -- as long as you can maintain contact, you are still pushing it, so it makes sense to follow through as long as you can. When you hit a person or a board, you're trying to hurt/break them, not push them: so you want to pack the energy of your blow into as short a time (and hence as large a force) as possible.
 

1. What is the concept of "contradiction in force*time applications"?

Contradiction in force*time applications refers to the inconsistency or conflict between two or more forces or factors that are applied to a system over a period of time. This can result in a discrepancy between the expected outcome and the actual outcome of a system.

2. How does contradiction in force*time applications affect scientific experiments?

Contradiction in force*time applications can significantly impact the results of scientific experiments as it can introduce errors and uncertainties. It can also lead to inaccurate conclusions and hinder the progress of research.

3. What are some common examples of contradiction in force*time applications?

Some common examples of contradiction in force*time applications include friction in motion, conflicting forces in mechanics, and conflicting factors in chemical reactions.

4. How can scientists identify and prevent contradiction in force*time applications?

Scientists can identify contradiction in force*time applications by carefully analyzing the forces and factors involved in their experiments. They can also use mathematical calculations and simulations to predict potential conflicts and adjust their methods accordingly.

5. Can contradiction in force*time applications be beneficial in any way?

While contradiction in force*time applications can cause complications in scientific applications, it can also lead to new discoveries and insights. By identifying and understanding these contradictions, scientists can gain a deeper understanding of the systems they are studying and potentially uncover new phenomena.

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