# 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?

## Answers and Replies

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

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

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.