Referring to your center of gravity please provide an explan

Referring to your center of gravity, please provide an explanation why changing the position of your limbs does not alter your path of flight. Which of the following statements is true? Muscles must create relatively large forces to produce practically effective torques about the joints. Muscle are arranged so that their moment arms about the joints are large. Muscle only need to create relatively small forces to produce practically effective torques about the joints. A 55 kg runner is running forward at 7 m/s when his foot strikes the ground. The vertical ground reaction force acting under his foot at this instant is 2000 N. The friction force acting under his foot is a 400 N braking force. What is the runner\'s vertical acceleration as a result of these forces? 26.6 m/s/s 36.4 m/s/s 2.7 m/s/s 3.7 m/s/s

Solution

1. By conservation of momentum, your center of mass would stay at the same place as all such forces that you apply are internal forces. External forces stay the same.

2. a. To balance torque when line of action of force is closer for internal forces as compared to the external forces.

3. Take only the vertical forces:

Force due to gravity = mg = 55* 9.81 N = 539.55 N

Ground reaction force in upward direction = 2000 N

Net force in upward direction = 1360.45 N

Hence acceleration = F/m = 26.6 m/s²