You are Here: Home >< Physics

# Force and energy watch

1. Is there an equation where you can work out the energy from the force?

I really can't think of one atm
2. Well, work done (so energy used) = Fx. Or do you mean something else?
3. (Original post by rsk)
Well, work done (so energy used) = Fx. Or do you mean something else?
Yeah, so you need the distance as well?
4. Well, if you could work out energy from force, with nothing else at all, then they'd be essentially the same quantity, wouldn't they?

So if that's what the OP is looking for, I guess the answer's no.
5. Energy = - integral Fdx

If you know F as a function of x, you can work out the energy function.
6. (Original post by teachercol)
Energy = - integral Fdx

If you know F as a function of x, you can work out the energy function.
But for AS/A level, can you think of anything else?
7. (Original post by Sentooran)
But for AS/A level, can you think of anything else?
Do you have an actual problem that you're trying to solve? It might help.
8. (Original post by generalebriety)
Do you have an actual problem that you're trying to solve? It might help.
I was referring to the original question at the top of this thread, which asked whether there were equations which related force to distance. teachercol gave a response, which was very good as usual, but beyond the AS syllabus. Hence, I asked him whether he knew any formulae which would relate force and distance, but at an AS standard.
9. (Original post by Sentooran)
I was referring to the original question at the top of this thread, which asked whether there were equations which related force to distance. teachercol gave a response, which was very good as usual, but beyond the AS syllabus. Hence, I asked him whether he knew any formulae which would relate force and distance, but at an AS standard.
Work done = force * distance. This is equivalent to integrating force with respect to distance, but only works for constant force.

I would have thought that was AS physics standard though. I don't do physics but it's certainly in maths.
10. (Original post by generalebriety)
Work done = force * distance. This is equivalent to integrating force with respect to distance, but only works for constant force.

I would have thought that was AS physics standard though. I don't do physics but it's certainly in maths.
Thanks.

That would be in Mechanics (in Maths), but definitely not in AS Physics, as they've taken pretty much all calculus out of it.
11. (Original post by Sentooran)
Thanks.

That would be in Mechanics (in Maths), but definitely not in AS Physics, as they've taken pretty much all calculus out of it.
Ah... unlucky.
12. (Original post by teachercol)
Energy = - integral Fdx

If you know F as a function of x, you can work out the energy function.
Are you sure its negative? It does not make sense to me to be negative.
13. Its all a question of which energy increases and which energy decreases.

If F is in the same direction as x, we have an attractive force, which means that KE increases and PE decreases.

The Energy in the equation is PE.

Its how we derive the formula for grav PE for example.
14. Infact energy is not just E(f,x) it is E(f,x,t) which is the same as E(p,t) which is the intergral Pdt.

as for the negative, that is a specific situation for example if a mass in a gravitational feild travles towards the body creating the field, then yes change in energy will be negative, but thats one specific case.
15. I'd say its a general relationship between any kind of force and potential energy.

I'm open to counter-examples.
16. Well, the case is that I am trying to work out how much energy is release from a wind generator. I managed to do a few simple calculations where the 'boat' (my experiment was about sails) was at an angle and when the wind generator was on, the downward force was equal to the force the generator was blowing out (hence the boat was not moving and the downward force i caluclated was equal to the force of the generator). This angle was at 11 degrees and the boat was 77cm away from the wind generator.

I understand that the wind will obey an inverse square law, but I was wondering if there was a way I could work out how much energy the wind generator gave out.

I hope that fills you all in a bit better
17. I doubt that it will obey an inverse square law. There seems no reason why the wind would spread out spherically.

Maybe an inverse (1/r) law if it spreads out cylindrically is more likely.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 1, 2006
Today on TSR

### Makeup, beauty and skincare

Best of Black Friday 2018

### University open days

Wed, 21 Nov '18
• Buckinghamshire New University
Wed, 21 Nov '18
• Heriot-Watt University