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# Work,energy and power watch

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1. A Particle of mass 5kg is pulled across a rough horizontal surface. The coefficient of friction between the body and the surface is 0.4 . Given that the particle moves with the speed 7ms^-1, find the work done against friction in 2 seconds.

I have managed to work out the force, through F=muew*R just having bit of trouble working out the distance, needed for W=F*S

Thanks
2. (Original post by DOJO)
A Particle of mass 5kg is pulled across a rough horizontal surface. The coefficient of friction between the body and the surface is 0.4 . Given that the particle moves with the speed 7ms^-1, find the work done against friction in 2 seconds.

I have managed to work out the force, through F=muew*R just having bit of trouble working out the distance, needed for W=F*S

Thanks
Constant speed, so a = 0, so no resultant force and so resistive force = pulling force = 5g*0.4 = 2g

in 2 seconds, distance is 14m, so work done = 14*2g.

Aitch

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Updated: May 16, 2005
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