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If under uniform motion in a straight line an object covers a distance of 8 m in 4 seconds what would be the net work done if the mass of the object is 2 kg?

What i don't understand is whether the initial velocity of the object should be considered 0 or as 2 m/s as the object is not accelerated?enter image description here

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  • $\begingroup$ @sammygerbil, about the object not being accelerated was indeed an assumption on my behalf, but what the question depicted was a distance and time graph. Would my assumption be wrong? $\endgroup$ – Anamika Ghosh Oct 21 '16 at 12:52
  • $\begingroup$ Is the distance-time graph a straight line? Or is this an assumption? Perhaps the velocity-time graph is a straight line? It would be helpful if you could post the question in full, exactly as printed. $\endgroup$ – sammy gerbil Oct 21 '16 at 13:04
  • $\begingroup$ @sammygerbil I have just uploaded the graph and it is a s - t graph $\endgroup$ – Anamika Ghosh Oct 21 '16 at 13:09
  • $\begingroup$ Yes this is a distance-time graph which shows constant velocity. Therefore the net force on the object is zero and no (net) work is being done. There is no mention of friction. Perhaps that is the answer which is expected : net work done is zero. $\endgroup$ – sammy gerbil Oct 21 '16 at 13:16
  • $\begingroup$ My question would be what would be the significance of the origin from 0 ? $\endgroup$ – Anamika Ghosh Oct 21 '16 at 13:27
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"Uniform motion" usually means constant velocity. However, if there is constant velocity then there is no change in kinetic energy hence no work done. Perhaps you mean there is "uniform acceleration"? You state that the object is not accelerated - is that what the question actually says, or is that your assumption?

If there is uniform acceleration (you will have to assume from rest, unless the question states otherwise), then I think you will be able to solve this easily. Work done = force x distance = increase in KE. (I think you must also assume there is no friction.)


If there is no acceleration, the net force on the object is zero. So the net work done on the object is zero.

Perhaps there is friction, and the question is asking what work is done against the force of friction? That is easily calculated as force x distance.

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  • $\begingroup$ the acceleration being 0 was my assumption for the question mentioned of a distance - time graph, so i guess the slope of the line must give the velocity and the acceleration must be 0 $\endgroup$ – Anamika Ghosh Oct 21 '16 at 12:59
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In my opinion the velocity of the object should be considered as 2 m/s since it is mentioned that the motion is uniform. The acceleration is zero.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – ACuriousMind Oct 23 '16 at 15:10

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