A teacher of 75.0 kg bungee-jumps (steps from rest) from a 100 m tower towards a river. The cord can stretch 40.0% of its unstrecthed length and has a breaking strength of 5000. N (if tension is greater than this, it snaps). The cord stretches .250 meters when a 10.0 kg weight is in equilibrium hanging from its end. If the teacher falls 35.0 meters before the bungee cord starts to stretch, will this become a free fall for the teacher, or will he bounce back? Support your answer will calculations and reasoning in words. Neglect air resistance.
To determine whether the teacher will bounce back or experience a free fall, we need to compare the maximum stretching of the bungee cord with the distance the teacher has fallen.
First, let's find the maximum stretching distance of the bungee cord.
The cord can stretch 40.0% of its unstretched length. This means that when the cord is fully stretched, it will be 140.0% of its original length.
Given that the cord stretches 0.250 meters when a 10.0 kg weight is in equilibrium, we can calculate the initial length of the cord as follows:
Unstretched length = stretched length / stretch percentage
Unstretched length = 0.250 meters / 0.40 = 0.625 meters
Now, let's calculate the maximum stretching distance of the cord:
Max stretching distance = unstretched length * stretch percentage
Max stretching distance = 0.625 meters * 0.40 = 0.250 meters
The maximum stretching distance of the bungee cord is 0.250 meters.
Next, we can determine the distance the teacher has fallen before the bungee cord starts to stretch. Given that the teacher has fallen 35.0 meters, which is greater than the maximum stretching distance of the cord (0.250 meters), the teacher will experience a free fall.
Therefore, the teacher will not bounce back and will continue to fall freely until the cord starts to stretch.