- #1

fog37

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- TL;DR Summary
- Mechanical power generated by a force F

Hello,

It is well understood that a constant horizontal force ##F_{applied}## applied to an object of mass ##m## over a distance ##d## in a direction that is not orthogonal to the direction of motion produces mechanical work ##W= F d ##.

This work is a mechanism to inject (or subtract) energy from the object (tow other two possible mechanisms are heat and electromagnetic radiation).

The force ##F_{applied}## produces an acceleration ##a_{applied}## and using one the kinematic equation we can determine the very exact time ##t## it takes the object to cover the distance ##d##. Mechanical power is defined as ##P = \frac {W}{t} = \frac {Fd}{t}##, so it seems that when a single force acts on an object, the power is always automatically determined since the the time ##t## over which the force acts during the displacement ##d## is fixed by the force. The force, through its acceleration, fixes the time it takes to produce the work ##W##, correct?

Another equivalent expression for power is ##P = F v##. Assuming the force ##F## is constant, the velocity ##v## will change linearly with time. This means that the expression ##P = F v## represents the

However, if the object was moving at a constant speed ##v## and several constant forces were acting on the object, the net force would be zero and the net generated power would also be zero.

The expression ##P = F v## would represent the power generated by a particular force ##F##. In this scenario, the time ##t## can be made to vary depending on the magnitude of the constant speed ##v## so the power produced by each force can vary while in the case of a single applied force the time ##t## is a very specific one fixing the value of the generated power.

Thanks!

It is well understood that a constant horizontal force ##F_{applied}## applied to an object of mass ##m## over a distance ##d## in a direction that is not orthogonal to the direction of motion produces mechanical work ##W= F d ##.

This work is a mechanism to inject (or subtract) energy from the object (tow other two possible mechanisms are heat and electromagnetic radiation).

The force ##F_{applied}## produces an acceleration ##a_{applied}## and using one the kinematic equation we can determine the very exact time ##t## it takes the object to cover the distance ##d##. Mechanical power is defined as ##P = \frac {W}{t} = \frac {Fd}{t}##, so it seems that when a single force acts on an object, the power is always automatically determined since the the time ##t## over which the force acts during the displacement ##d## is fixed by the force. The force, through its acceleration, fixes the time it takes to produce the work ##W##, correct?

Another equivalent expression for power is ##P = F v##. Assuming the force ##F## is constant, the velocity ##v## will change linearly with time. This means that the expression ##P = F v## represents the

*instantaneous*power. So in the case of a single constant force ##F_{applied}## the generated power increases linearly with time since ##v## increases linearly with time.However, if the object was moving at a constant speed ##v## and several constant forces were acting on the object, the net force would be zero and the net generated power would also be zero.

The expression ##P = F v## would represent the power generated by a particular force ##F##. In this scenario, the time ##t## can be made to vary depending on the magnitude of the constant speed ##v## so the power produced by each force can vary while in the case of a single applied force the time ##t## is a very specific one fixing the value of the generated power.

Thanks!