Q. A potential difference of 90 mV exists between the inner surfaces of a cell membrane. The inner surface is negative relative to the other surface. How much work is required to eject a positive sodium ion (Na+) form the interior of the cell?
Q. A student (m=75 kg) falls freely from rest and strikes the ground. During the collision with the ground, he comes to rest in a time of 0.040 seconds. The average force exerted on him by the ground is +18000 N, where the upward direction is taken to be the positive direction. From what height did the student fall? Assume that the only force acting during the collision is that due to the ground.