So if force =mass * acceleration, then an object moving at a constant velocity has zero acceleration, and thus force = zero.
So is f=ma actually mean net force or some other definition?
And I’ve been told work is force * distance, so sn object moving at a constant velocity would also have zero work? Which doesn’t sound correct so I’m confused on what exactly work defines
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Force is a definition. We define force as the change of momentum. Momentum is p=mv and the change so d/dt mv = ma as the change in velocity is acceleration and we define force to equal that ma. F:=ma.
An object moving with a constant velocity has no net force acting on it. It has momentum, if that momentum changes forces acted on the object.
Work is about doing stuff. If you want to pull a bucket from a vell then you need to do work on the bucket. If you shoot an arrow up with a constant velocity to get the bucket out, as the arrow pulls the bucket it will slow down, there is a change in momentum, there is a force, and the bucket moves up so work has been done. Work is the change in momentum over a distance. So you can apply a large force over a short distance or a small force over a longer distance the amount of work is the same.
So for the bucket example you have some wheel to turn to pull it up, pulling the bucket up you have to do work against gravity. If you pull the bucket up to height h. You need to do W=mgh amount of work. You can do it with a small wheel and then you’ll have to apply a lot of force. But with that force you will only need to turn the wheel a short distance. With a larger wheel as you apply more torque with it you apply a smaller force but over a longer distance. The result is the same Fs=mgh.
Yes an object just travelling with momentum p doesn’t do work, it does work when its momentum changes d/dt p. Which is what we defined a force to be. The latger distance that force is applied over the more work has been done.
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