Circular Motion Problem w/ Conservation of Energy

AI Thread Summary
The problem involves a physics teacher swinging from a 24m rope, starting from rest, and determining the height above the ground when the rope breaks due to excessive tension. The key equations include kinetic energy (Ek), gravitational potential energy (Eg), and centripetal force (Fc). The teacher's initial potential energy is calculated as 235.2m, and the velocity at which the rope breaks is linked to the condition that the tension in the rope must not exceed twice the teacher's weight. To solve the problem, the relationship between centripetal force and the velocity must be applied, considering what provides the necessary centripetal force at the breaking point. Understanding these dynamics is crucial for determining the height at which the rope fails.
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Homework Statement


Your favourite physics teacher who is late for class attempts to swing from the roof of a 24m long rope as shown in the picture. The teacher starts from rest (Ek=0) with the rope horizontal, but the rope will break if the tension force in it is twice the weight of the teacher. How high is the swinging physics teacher above the ground when the rope breaks?
(Hint: Use the conservation of energy)
CM2.png



Homework Equations


Ek=(1/2)mv^2
Eg=mgh
Fc=(mv^2)/r

The Attempt at a Solution


My diagram:
CM2-1.png

Eg = mgh
= m(9,8)(24)
= 235.2m
Ek = (1/2)mv^2
= mv^2
(because it says that the rope will break if the tension force in it is twice the weight of the teacher)
then i equate these.
235.2m = mv^2
235.2 = v^2
v = 15.3 m/s.
from here i have no idea what to do. i think i might have to use Fc=(mv^2)/r, but i not sure how.
thanks in advance for you help.




 
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What you have calculated is the velocity for which the kinetic energy is twice the initial potential energy. It's not that useful or related to your problem.

You already mentioned Fc=mv^2/r. How does this play a role in your problem?
What supplies the centipetal force and what is the condition that the rope breaks?
 
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