If there is just one force acting on an object, does its work necessarily result
ID: 2134912 • Letter: I
Question
If there is just one force acting on an object, does its work necessarily result in an increase in kinetic energy? Explain. (Select all that apply.)
Yes, when a force does work on an object it always results in an increase in kinetic energy.
No, if there is a force component along the line of motion, the force could act opposite to the motion and cause a decrease in kinetic energy.
The work done by the force on the object might result in an increase in kinetic energy.
No, if the force is at right angles to a body moving in a circular path, this centripetal force does no work and cannot change the kinetic energy.
Explanation / Answer
Yes. In which case A = F/M; so that V = U + AT = U + (F/M)T.
As you can easily see, the end speed V after accelerating A for T time when starting at initial speed U is continuously increasing. And because kinetic energy KE = 1/2 MV^2 where V is the same end speed, you can see KE is also increasing.
In fact, because V^2 = 2AS when starting from zero speed, we can show that KE = 1/2 M2AS = MAS = FS = work from the work function. In other words, the work we put on the mass M results in that kinetic energy.
If only one force is acting on an object, then the velocity of the object is necessarily changing. However,
the kinetic energy of the object is only dependent upon the magnitude of its velocity (its speed). As a
result, if the force only acts to change the direction of the object