The problem involves calculating the vertical velocity and force exerted by a boy during a jump. The boy has a mass of 82 kg and achieves a vertical leap of 1.2 m. Participants are tasked with finding the initial vertical velocity required to reach this height and the force exerted during a 30 cm lift after crouching.
Some participants have shared their calculations for the initial velocity and the force exerted during the jump. There is an ongoing clarification regarding the distinction between net force and the force exerted by the ground, indicating a productive exploration of the concepts involved.
Participants are discussing the implications of using different values for acceleration and the need to separate forces acting on the boy during the jump. There is uncertainty about the correctness of the calculations presented.
good!kooh said:I got sqrt of 23.52 for the initial velocity when he is standing up straight
you multiplied it by his mass, not his weight, and what you ended up with was the net force acting on him during the 30 cm 'squat' motion. But the net force includes both the force of the ground pushing up on him and his weight acting down on him. You need to separate out the 2 to find the pushing force of the ground on him.As for the force he applied when lifting the 30 cm after crouching I got,
3214.4N
for the 3214.4N , I found the acceleration he had during the 30 cm or .3m then multiplied it by his weight. I had v1 as 0 for this part.
Not sure if its 100% right tho