andy, when it said on the question... if the cat was dropped from the 6th floor, when would it hace half of its kinetic energy, is that just halving the number of the floor?, or is it a trick question?
and another one. the question about the men lifting bricks. how would you know which one does more power, because they don't give you any magnitudes to have you calculate...
meli
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Hiya Meliii
Definitely not a trick question. I think you mean question 16 right.
A year 10 pupil is dropped out of the window of the 6th floor. How much kinetic Energy does he have when he's halfway down as a fraction of his initial potential energy?
It's purely logical.
It's actually a question about work done really.
If the pupil falls half the distance then he will have only half the amount of Potential Energy. What happens to that potential energy? It is work done by the falling person right...
As it is assumed to be perfectly efficient energy transfer...
Then all of the PE is converted to KE.
So the PE is half of what it was
...so the KE must also be half of the initial PE!
It's not a trick question - it's just logical!
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