When a person pushes up a weight like in this picture http://www.freefitnessguru.com/Anato...20combined.jpg the weight is exerted on the wrist. So when the weight is stationary, the downwards force acting on the wrist is equal to the weight of the object. However, when he starts lifting it up, would this downwards force remain the same just that now the upwards force on the wrist>downwards force by the weight of the object?
While what if the wrist cannot handle the weight so it might snap. So in this case the wrist would be the weakest link here. But for example if a weak person loads too much weight, and the bone structure/muscles in the wrists can handle the forces however the triceps and shoulder (primary movers) cannot handle the weight then now they would be the weakest link?
When a person punches a bag, we would use the formula Δmv/t so a person punches at v1=10m/s and stops at 0m/s. But what would be the m? Would it just be the fist? Because the hips are also being used in the punch so I'm not sure which m to use. Would it just be the fist? If not what should it be?
Thanks in advance
While what if the wrist cannot handle the weight so it might snap. So in this case the wrist would be the weakest link here. But for example if a weak person loads too much weight, and the bone structure/muscles in the wrists can handle the forces however the triceps and shoulder (primary movers) cannot handle the weight then now they would be the weakest link?
When a person punches a bag, we would use the formula Δmv/t so a person punches at v1=10m/s and stops at 0m/s. But what would be the m? Would it just be the fist? Because the hips are also being used in the punch so I'm not sure which m to use. Would it just be the fist? If not what should it be?
Thanks in advance