A small ball of mass m is projected with a minimum horizontal velocity v0 on a smooth wedge of mass M so that it will reach the highest point P of the wedge. The value of v0 come out to be √(a+4mM)gR. Find the value of a.
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Solution
If the ball reaches at point P, the velocity of the ball with respect to wedge should be √gR. Using work-energy theorem from centre of mass frame at A and the highest point P Wext+Wint=Wext+0=(ΔK)cm Wgravity=(ΔK)CM −mg(2R)=[12μv2rel]final−[12μv2rel]initial −−mg2R=12μ(V+v)2−12μv20 (i)
μ=(mMm+M) and v=√gR As there is no external forces acting on the system in horizontal direction. The linear momentum of the system should be conserved. i.e., mv0=m(V−v)+MV ⇒V=m(v0+v)(m+M) (ii) From equations (i) and (ii), we get ⇒v0=√(5+4mM)gR