Jump higher?

  • Thread starter romsofia
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  • #1
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Hi, do you jump higher when you run and jump, or just stand and jump?

I believe you jump higher if you run and jump.
 

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  • #2
rcgldr
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Run and jump would be higher. The highest would be a gymnastic type flip flop move into a high back dive or flip. Two foot take offs are not allowed in high jump contests though.
 
  • #3
tiny-tim
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Hi romsofia! :smile:
Hi, do you jump higher when you run and jump, or just stand and jump?

I believe you jump higher if you run and jump.
I think the running part is primarily because you need to move your centre of mass horizontally far enough to clear your body of the bar.

If you approach almost sideways, you can get away with a very slow run, since you only have to move a distance slightly greater than the width of your shoulders or hips.

But if you approach almost head-on, you need to run much faster, since you have to move a distance comparable with your height.

Since the human body has no way of converting KE to elastic PE (and since neither shoes nor the ground can store much elastic PE), it is almost impossible to convert the extra "horizontal KE" from running into elastic PE and then back again to "vertical KE" … so extra horizontal speed doesn't help produce extra vertical motion.
 
  • #4
rcgldr
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Since the human body has no way of converting KE to elastic PE (and since neither shoes nor the ground can store much elastic PE), it is almost impossible to convert the extra "horizontal KE" from running into elastic PE and then back again to "vertical KE" … so extra horizontal speed doesn't help produce extra vertical motion.
A better analogy would be that a person uses his leg or legs as mostly inelastic vaulting poles. In the case of the gymnastic move I mentioned angular KE is used in addition to linear KE.
 
  • #5
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A better analogy would be that a person uses his leg or legs as mostly inelastic vaulting poles. In the case of the gymnastic move I mentioned angular KE is used in addition to linear KE.
I agree, it is possible to convert some of the horizontal kinetic energy into vertical kinetic energy by placing the leg (or two legs) at an angle (lower than 90 degrees) to the ground, absorbing the radial kinetic energy and keeping tangential kinetic energy (which has a positive vertical component). The principle is similar to a pole vault (leg working as a pole), which can work even with a pole that only absorbs radial kinetic energy, without returning it elasticly - of course the effect is weaker than in case of the elasic pole.

Also I am certain that when jumping with with two foot take off+horizontal speed anyone can jump higher than with two foot take off from rest. With the right technique even one foot take off with horizontal speed might be higher than two foot take off from rest.
 

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