Atennis player who is recovering from an ankle injury and is not allowed to change directions can maintain her cardio fitness level by

A tennis player who is recovering from an ankle injury and is not allowed to change directions can maintain her cardio fitness level by using the rowing machine, the stationary bike with one leg, or swimming. These activities do not require a change in direction. These activities will not give strain to the injured part.

The answer is 4f======since electrostatic force is given by    we let f be the electrostatic force when  r = 1 m    if we let  denote the electrostatic force when the distance is decreased so that r = 0.5m, then    we established earlier that f = kq₁q₂. therefore    the force will now be 4f.

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.