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![[Post New]](/templates/default/images/icon_minipost_new.gif) 7 Feb 2007 20:29:32 IST
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A body of mass 10kg at rest is acted simultaneously upon by 2 forces 4N &3N at right angles to each other, whats its kinetic energy at end of 10 secs.
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7 Feb 2007 20:31:59 IST
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Net resultant force acting on the block =  3 2+4 2=5 N. So the net acceleration of the block=5/10=1/2m/sec2 now v=at=1/2*10=5m/sec. So KE=1/2*m*v2=1/2*10*25=125 J So the result is 125 J
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7 Feb 2007 20:35:49 IST
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yes it is 125 J
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7 Feb 2007 20:41:14 IST
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since F=ma; therefore As resultant force is 5N by vector law of llgm therefore a= .5 m/sec therefore velocity after 10 secs is 5 m/sec Now K.E is .5mv2 Therefore k.e is125 Joule
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9 Feb 2007 12:55:59 IST
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all of you are correct.. and we can use the impulse approach too.. Impulse given by the 5N force in 10 sec is 50Ns, and this is equal to change in momentum. As initial momentum is zero, final momentum is 50Nm. Now either get v = 50/10 = 5 and get KE, or directly remembe KE = p2/2m
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Sudeep Kumar
(B tech, IITd)
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