Question

please help me


An 80.0 kg hiker walks a distance of 400.0 m along a road that slopes 5.0 degrees upward, and then stops. What is the hiker's final gravitational potential energy relative to her original position? You may use a trigonometry table.


784 J

3.9 × 103 J

2.7 × 104 J

3.1 × 105 J

Answer 1

i need help with the formula to figure it out, if someone can help please do.

Answer 2

Firstly, model the problem. If the road is 400 m at 5 deg. You must assume the curvature of the earth is 0. Try drawing the problem with the draw tool and post it here.

Answer 3

:-)

Answer 4

the next thing i'm struggling with is the equation
i have it all wrote down
even some that i probably dont need

Answer 5

http://openstudy.com/study#/updates/52799e1ae4b0e2d057c3428a helpppppppp

Answer 6

Ok, next try to find the height of the road. Do you know how to use trigonometry? Use the SOHCAHTOA acronym
Sin = Opposite/Hypotenuse
Cos = Adjacent/Hypotenuse
Tan = Opposite/Adjacent

Answer 7

i know some trig but i don't understand the entire thing.

Answer 8

you can use sin to find the height of the right triangle you drew.
Sin is Opposite/Hypotenuse so take the sin of the angle and multiply it by 400 m

Answer 9

you should get 34.9 m

Answer 10

okay i did.

Answer 11

34.9
and now what

Answer 12

and what is the 34.9

Answer 13

Now you need the formula for potential energy.

Answer 14

PEgrav = mass • g • height

Answer 15

cool, all you have to do is plug in your quantities and check your units. Energy is given in
\[1 J = 1 Kg \times (m/s)^{2}\]

Answer 16

can you tell me what that all stands for
pe grav and g
i mean

Answer 17

g = 9.8 m/s i think

Answer 18

PEgrav is energy stored when a heavy object is pushed up a hill. Because of the principle of "conservation of energy", the energy of a system is constant unless there is energy added or subtracted.

Answer 19

i don't know what im doing
so my final equation would be 80 * 9.8 * 34.9 righ?

Answer 20

When the 80 Kg hiker (who is pretty heavy for someone who likes hiking in the outdoors) moves up the inclined road, he/she adding vertical potential energy to his/her body.
Imagine taking a penny up on an elevator ride to the top of a building. The elevator does work and adds potential energy to the penny, measured in fractions of a Joule (say .01 J).
When you throw the penny off of the building, the penny looses energy while it drops; the loss of potential energy is converted into speed (or, to be very accurate, it turns into momentum), and when the penny hits the concrete it transfers all it's energy to the concrete (unless it hits somebody in the head!).

Answer 21

you are right about your final equation

Answer 22

so i got like 27000ish

Answer 23

right. so, I was asking myself why none of the answers you listed is 27332J. Is it possible that you listed J when you should have listed KJ (kilo joules)?

Answer 24

hmmm. Our answer is off by a factor of 100 and I don't know why :-(