Question related to energy

thegame

here is a question that I am unable to solve:

The average human, of mass 52 kg needs to have approximately 9,000,000 J of energy per day. Suppose, you had to walk up a hill with an incline of 12 degrees. Determine the following:
a) how high would the hill have to be (i.e. - change in height) in order to consume all of this energy.
b) how much work did gravity do in all of this walking?

for A, i know you have to use the formula Eg=mgh but i am not sure where to sub in the energy as 9,000,000J or sin 12*9,000,000 (since its at an angle)

B) i dont knoe what role gravity plays in this?

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Ambitwistor

In the formula mgh, h refers to just the vertical displacement, not the total distance.

For the work, you need to consider the definition of work done by a force (in this case, gravity) -- or, equivalently (in this case), the work done by changing potential energy.

thegame

Re: Re: question related to energy

Originally posted by Ambitwistor
In the formula mgh, h refers to just the vertical displacement, not the total distance.
sorry, but you haven't answered my question? directly

Ambitwistor

Re: Re: Re: question related to energy

Originally posted by thegame
sorry, but you haven't answered my question? directly
Energy is energy. You don't multiply it by anything.

thegame

SO, energy is not a vector quantity?

Ambitwistor

No, energy is a scalar.

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