Simple Conservation of energy question

[haruspex]

Extra energy technically isn't coming from somewhere, It's just saving of energy to use it in a good cause that is stretching more.

I don't understand. Rising the extra 0.4m requires energy. It must come from somewhere.
What is being stretched, exactly?

 

[Derek1997]

It's because of COM, no COM more energy to raise ur body.

 

[haruspex]

It's because of COM, no COM more energy to raise ur body.

I have no idea what you mean.

 

[Derek1997]

Sorry for inconvenience, I meant since the center of mass wouldn't be within the athlete's body during the jump (he is in the air) hence, It's easier for him to cross the bar. Easier to move his legs and etc.

 

[jbriggs444]

Sorry for inconvenience, I meant since the center of mass wouldn't be within the athlete's body during the jump (he is in the air) hence, It's easier for him to cross the bar. Easier to move his legs and etc.

Can you explain why you think that any of that is true or how you think any of that works?

 

[haruspex]

center of mass

Are you considering the pole as part of that mass? If so, don't. We are assuming the pole's mass is negligible, and if we were to allow for its mass that will make it harder since some of the pole's mechanical energy will have gone into raising the pole to the vertical.

You are right that the athlete's mass centre may be external, but can you explain how, exactly?

 

[Derek1997]

Are you considering the pole as part of that mass? If so, don't. We are assuming the pole's mass is negligible, and if we were to allow for its mass that will make it harder since some of the pole's mechanical energy will have gone into raising the pole to the vertical.

You are right that the athlete's mass centre may be external, but can you explain how, exactly?

To maximize vault height, vaulters bend their body around the bar (as shown in the figure below). In doing so, their center of mass (the red dot) can actually pass underneath the bar, while enabling their body to pass over the bar (the black dot). This means that the bar can actually be placed higher than the maximum height reached by the center of mass of the vaulter.pole vaulters do not use their strength to lift themselves over the bar. Instead, they primarily use the pole as an intermediate tool to help them convert their kinetic energy into gravitational potential energy (height). Good sprint speed combined with good gymnastic ability are what is needed to effectively utilize the pole.Air resistance also plays a role in how high a vaulter can vault. In areas of higher altitude, the air is less dense which reduces air resistance when running. This in turn means that the vaulter can reach a higher speed before the vault, which results in a higher vault. To give you an idea, if a vaulter running at 10 m/s at sea level can run 2% faster at high altitude, then he can vault about 21 cm higher at high altitude. enough?

 

[Derek1997]

I hope that can explain part B?

 

[haruspex]

I hope that can explain part B?

That (passing the mass centre below the bar) is certainly part of it, but I doubt it would get another 0.4m. You are still missing an important component hinted at in several posts.
Look at the position of the vaulter's body in relation to the part of the pole the vaulter is holding. How does this change in going from ground level to going over the bar?

 

[Derek1997]

That (passing the mass centre below the bar) is certainly part of it, but I doubt it would get another 0.4m. You are still missing an important component hinted at in several posts.
Look at the position of the vaulter's body in relation to the part of the pole the vaulter is holding. How does this change in going from ground level to going over the bar?

Horizontal velocity to vertical velocity change?

 

[haruspex]

Horizontal velocity to vertical velocity change?

No, not velocity; position.