Consider an elliptically shaped rail PQ in the vertical plane with OP = 3 m and OQ = 4m. A block of mass 1 kg is pulled along the rail from P to Q with a force of 18 N, which is always parallel to line PQ (see the figure given). Assuming no frictional losses, the kinetic energy of the block when it reaches Q is (n × 10) Joules. The value of n is (take acceleration due to gravity = 10 ms–2)
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F is constant
⇒ WF = F × 5 = 90 J
wgr = –mgh = –1 × 10 × 4 = – 40 J
90 – 40 = K = 50
n = 5