In: Physics
When bungee jumping from a high bridge over Victoria Falls, an operator first attaches an elastic rope to the jumper. The jumper then jumps off the bridge, falling freely until they reach the unstretched length of the rope. Then, the rope begins to stretch and slows the jumper to a stop. The rope pulls the jumper back up, and they oscillate up and down for a while until the operator pulls the jumper back up to the bridge. A. The rope is essentially a long spring. Let's label the jumper's mass m, the unstretched length of the rope L0, the height of the bridge above the water H, the elastic (spring) constant of the rope k, and the gravitational field strength g. The jumper's speed at the point where they've fallen the full length of the unstretched rope is a maximum, vmax. For simplicity, we will neglect resistive forces like air drag.
A. The jumper has a mass of 55 kg, and the bridge's height above the river is 150 m. The rope has an unstretched length of 9 m and stretches a distance of 6 m before bringing the jumper to a stop. Determine the maximum speed of the jumper and the spring constant of the rope. In your calculation, use g = 10 N/kg.
1) vmax = _____ m/s ?
2) k = _________ N/m ?
B. Now suppose the jumper has a mass of 80 kg. Do you think the maximum speed of the jumper will increase, decrease, or stay the same? Will the rope need a larger, smaller, or the same spring constant to bring the jumper to a stop in the same distance as part D?
1) The maximum speed of the jumper will?
2) The rope will need a spring constant that is?
C. Now calculate the maximum speed of this more massive jumper and the spring constant of the rope needed to bring the jumper to a stop after the rope stretches 6 m. (Again, use g = 10 N/kg for your calculations.) Were your predictions correct?
1) vmax = _____ m/s ?
2) k = _____ N/m?