Q.

Consider an elliptical shaped rail PQ in the vertical plane with OP=3 m and OQ=4 m. 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)                     [2014]


Ans.

(5)

Work done = Increase in P.E. + gain in K.E.

F×d=mgh+gain in K.E.

18×5=1×10×4+gain in K.E.

 Gain in K.E.=50 J=10n  n=5