L1 Mechanics NZCE Exams 2011

QUESTION THREE: ROPE CLIMBING

A girl of mass 60 kg uses 5100 J of energy when she climbs a vertical rope.

(a) Calculate the maximum height it would be possible for the girl to reach.

(b) In reality, the girl reaches a height of only 8 m.

Explain why the energy used by the girl during the climb does not equal the work she does to reach the vertical height of 8 m.

In your answer you should:

• name the type of energy the girl has when she is 8 m above the ground

• calculate the work done to reach a height of 8 m above the ground

• calculate the difference between the work done and the energy used by the girl

• explain where the “missing” energy has gone, and why this occurs.

Supplementary Questions

1. Should the Work Done be same with Energy used? 
1. Work Done equals to the Energy used only at no energy loss (on friction, air resistance, etc.)
2. Why Work Done equals to Energy used?
1. It may be not equal, see 1.
3. Energy Gained vs Energy Used
4. Energy Gained vs Work Done  

Control Questions:

1. At Work Done, is energy used or gained?