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MBBphys
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Homework Statement
I was just wondering whether the following notes I took on work in physics are accurate? Or have I got my understanding wrong?
Note on friction
Following from the example of the dragging object above…
The object stops because it loses kinetic energy due to friction.
How does the friction force do work?
Ok, so I push an object, then let go; I have transferred kinetic energy to it.
Now it moves a certain distance in a direction opposite to friction force acting on it.
So, in W=Fd, F will have a negative sign as it is in the opposite direction; the magnitude of F is the magnitude of the friction force.
Hence, energy transferred will come out with a negative sign.
What does that mean?
The W=Fd formula tells you that if you move something with a force, you are transferring some energy INTO THAT OBJECTàthe fact that W is negative here is because the point of application of force is losing energy; the kinetic energy of the object is being transferred out as heat energy (primarily), BECAUSE THE FORCE IS ACTING OPPOSITE TO THE DIRECTION OF MOVEMENT.
If W has a positive sign, that means we are transferring energy INTO the object the force is acting on to make it move; if W is negative, energy is being transferred out.
Thanks; your help would be much appreciated! :)
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