An object is on a horizontal surface with friction. We pull the object with a st

Question

An object is on a horizontal surface with friction. We pull the object with a string so that the objects speed increases all the time

a) Net work done on the object is zero

b) Net work done on the object is larger than 0 (that it’s positive)

c) Net work done on the object is smaller than zero (that it’s negative)

d) Net work may be positive or negative depending of chosen positive direction

My thought: these’s friction but since the speed always increase the pull force must be larger than the friction force. Only one option to choose

Work is positive if force applied and direction is the same way. Is this the only thing I have to think about?. What if force and direction is to the left, but I define positive to the right, Is than the work negative. Or can we always say that as long as net force and direction is the same way, work is always positive?

Explanation / Answer

You are thinking way too much,Its actually pretty simple,The object is accelerating in the direction of the applied force because there are only two forces acting on the body.The other one is friction which can't make the body accelerate.So the work done by the Force applied on the body is positive.

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