Fuckin’ energy, how do they work? (I’d like to speak to a scientist, I promise I won’t get pissed)
In: Physics
“Force” is just a push or a pull. Force is measured in newtons. One newton is roughly the force you need to lift a bar of soap.
But just because you push on something doesn’t mean it’ll actually move. Applying a force to an object as it moves will “do work” on it, and change its “energy”. Work and energy are measured in Joules, and one Joule is one newton times one meter — it’s roughly how much work you have to do to lift a bar of soap to waist height.
Energy comes in many forms: pushing on an object may increase its speed, or lift it up in the air, or heat it up, etc. Energy is a useful idea because it’s “conserved”: energy can change from one form to another, but the total amount stays the same.
For me, the confusing thing was the difference between torque and energy, because they are kind of the same in units. Both of them are actually Newton * meter, but sometimes you write them as Newtonmeter [Nm] and sometimes as Joule [J].
Imagine a door which is 1m wide. If you apply a force of 1N to the side opposite of the hinges, you’re applying a torque of 1Nm. If the door doesn’t move, no energy is transferred. But the torque applied to the hinge is 1Nm. The hinges have “to hold” against the torque applied, otherwise the door would move.
If the door does move by 1m, then you’ve done work which requires energy – if you move an object by 1m using 1N of force, then the energy you’ve needed is 1J. Note that this time, the meter doesn’t come from the width of the door, but from the distance it moved.
1 Newton is a force. Specifically the force to accelerate 1kg at 1m/s^2
1 Joule is an energy. The energy transfered when applying 1 Newton on an object during whatever time it takes to move it 1 meter.
1 Watt is the work done by an object under an energy. This is harder to understand, but is the energy change per unit of time. It’s not the same gaining 1 Joule in 1 sec than in 10 sec.
Energy is only transfered when you move the object, and depends on during how much distance the force was applied.
Example: you can’t push horizontally a heavy object on the ground (say a tank) due to the friction of the floor or lift vertically due to how heavy it is in our gravity. If it doesn’t move, you have lost energy as heat, but have transfered no movement/energy to the tank.
This is an “everyday” example with newtons and joules, involving mechanic energy, but energy and forces can be of different types
Edit: added work. Can’t believe I’m supposed to know this but took me 45 min to write for eli5
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