Asked by Mia :)
Hi! This question isn't necessarily checking work, but more of some help figuring something out. In science, we are learning everything about energy. I am currently on a test, but I can't figure out how to calculate potential and kinetic energy. They gave me numbers, and I know that my answer will be in J's. Can anyone tell me how to calculate energy? thank you! :-)
Answers
Answered by
DrBob222
K.E. = 1/2*m*v^2
P. E. = mgh
P. E. = mgh
Answered by
Damon
Oh my.
Well, there are three sorts that you may be working on:
1. Potential energy
This includes gravitational potential energy, usually simplified as m g h close to the surface of earth where m is mass in kilograms and g is gravitational acceleration, about 9.81 m/s^2 on earth surface. h is height difference in meters up from whatever you define as zero energy height. As you said, meters, seconds, kilograms yields Joules. You may also see the universal formula force = G M1 M2 / d^2 between any two objects a distance d apart and with masses M1 and M2. Google that law of gravitation.
Potential energy also is in a spring when you compress it or stretch it. That is in general (1/2) k x^2 where k is the "spring constant" and x is the distance from un- stretched length.
There are many other forms but I think these are the two you are most likely to see until you get to electricity etc.
2. Kinetic energy
You will probably see this as (1/2) m v^2 where v is the speed of the masd m. With circular motion this is expressed usually as (1/2) I omega^2
where I is the"moment of inertia " and omega is the angular velocity. This is really the same old (1/2) m v^2 but put in a form that is easily used for rotating objects.
3. Heat energy
You are likely to see this as just lost Joules due to friction or whatever.
In a perfect system the total kinetic and potential energy, for example (1/2) m v^2 + m g h is constant. However if there is friction then something heats up and mechanical energy is lost to heat energy.
That is very simplified but what I have a hunch you need immediately.
Well, there are three sorts that you may be working on:
1. Potential energy
This includes gravitational potential energy, usually simplified as m g h close to the surface of earth where m is mass in kilograms and g is gravitational acceleration, about 9.81 m/s^2 on earth surface. h is height difference in meters up from whatever you define as zero energy height. As you said, meters, seconds, kilograms yields Joules. You may also see the universal formula force = G M1 M2 / d^2 between any two objects a distance d apart and with masses M1 and M2. Google that law of gravitation.
Potential energy also is in a spring when you compress it or stretch it. That is in general (1/2) k x^2 where k is the "spring constant" and x is the distance from un- stretched length.
There are many other forms but I think these are the two you are most likely to see until you get to electricity etc.
2. Kinetic energy
You will probably see this as (1/2) m v^2 where v is the speed of the masd m. With circular motion this is expressed usually as (1/2) I omega^2
where I is the"moment of inertia " and omega is the angular velocity. This is really the same old (1/2) m v^2 but put in a form that is easily used for rotating objects.
3. Heat energy
You are likely to see this as just lost Joules due to friction or whatever.
In a perfect system the total kinetic and potential energy, for example (1/2) m v^2 + m g h is constant. However if there is friction then something heats up and mechanical energy is lost to heat energy.
That is very simplified but what I have a hunch you need immediately.
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