# High Jumper Physics Question

1. Mar 29, 2005

### vietknight

With what minimum speed must a high jumper leave the ground to raise his center of mass by 2.10m and cross the bar with a speed of 0.8m/s?

For this question, I'm not sure how to proceed, and if its surely the correct way to do so but here's what I've done.

Since the jumper is crossing the bar at 0.8m/s, I know that the vertical vector is 0.8m/s. But the diagonal vector, similar to one in a horizontally launched projectile, I am having trouble determining. I feel there is not enough information for me to answer this question. If I knew the distance travelled, or time in the air, or even an angle of launch it might be able to lead me somewhere. Anyone see a solution with only those values given?

thx

2. Mar 30, 2005

### vietknight

Nevermind, I found the answer, mass is negliable because it doesn't affect the falling speed of the object. All things fall at the same rate due to the constant gravity. Just like, if you have a frictionless ramp, there is nothing opposing the object from rolling down it, hence its similar to an object in free fall.

I got my ans outt o 6.47m/s if you guys wanna do it yourselves.