Cutter Ketch said:I can see how that would be confusing. There are several things going on. First is the distance over which the athlete pushes. The muscles can only generate so much force and so only so much acceleration. If you can't increase the force any more what can you change to achieve more vertical velocity? If the athlete can push for a longer distance they accelerate for more time and reach a higher vertical velocity. So they start with the center of gravity as low as they can (as low as they can still generate a significant force that is) and they push until their center of gravity is as high as they can get it. Accelerating that whole time and distance they achieve the highest vertical velocity.
Force times time is impulse. That is the change in momentum and since the mass doesn't change goes directly to velocity. Force times distance is energy and is also connected directly to velocity.
The hands up increases the height of the center of gravity as I have said. However getting to the highest point does more than just increase the pushing time. As soon as the feet leave the ground you are done pushing. Your center of gravity will fly in a parabolic arc until you touch back down. You want that starting point to be as high as possible. Raising your arms and stretching your toes to raise your COM another inch is like jumping from a platform that is that much above the ground.
The final important thing is which muscles do the jumping. Going from a crouched position to stretched out as high as you can reach involves a lot of muscles. All of those movements pushed the center of mass higher. All of those movements accelerated the body upward, and so much more muscular energy goes into the jump than if you jumped with... say ... your calf muscles alone
Hope that helps
It does not allow them to push off with greater force; it allows the force to be applied for longer, so reaching a higher take-off speed.ravsterphysics said:why does moving their centre of gravity to a lower point allow them to push off with more force?
Good technique will make the height cleared as high as possible for a given height of mass centre, but for a given technique the higher the mass centre the higher the bar cleared.ravsterphysics said:why does centre of gravity need to high for them to reach a higher point? If you look at this video (2 mins 42 seconds) you can see that the jumper attains a higher jump but their centre of gravity is lower than them:
The centre of mass/gravity is the point at which the entire mass of an object can be considered to be concentrated. This point is determined by the distribution of mass within the object.
The centre of mass/gravity is important because it is the point around which an object's weight is evenly distributed. This point is used to calculate an object's stability, and is crucial in understanding the motion and behavior of objects.
The centre of mass/gravity is calculated by finding the weighted average of the individual masses within an object. This is done by multiplying each mass by its distance from a reference point, and then dividing the sum of these values by the total mass.
Yes, the centre of mass/gravity can change depending on the distribution of mass within an object. For example, if more mass is added to one side of an object, the centre of mass/gravity will shift towards that side.
The centre of mass/gravity directly affects an object's stability. If an object's centre of mass/gravity is located within its base of support, it will be stable. However, if the centre of mass/gravity is outside of the base of support, the object will be unstable and may tip over.