1.

Consider an arrangement shown in the figure. The pulley P is frictionless and the threads are massless. The mass of the spools is m and moment of inertia of the spool is 1/2 mR^(2). The mass of the disc of radius R is also m. The surface below the spool is rough to ensure pure rolling of spool. the mass of the block is m and the surface below the block is smooth. find the initial acceleration of the block when the system is released from rest.

Answer»

`4/37 g`
`2/37 g`
`8/37 g`
`10/37 g`

Solution :SUPPOSE the acceleration of the block `B` is a, acceleration of disc is `a_(2)` and the acceleration of centre ofmass of spool is `alpha_(1)`. Also suppose the angular accelerations of spool and disc are `alpha` and `alpha_(2)` respectively.

Now `alpha=alpha_(1)(R-R/2)`
`rArralpha=(alpha_(1)R)/2....(1), alpha_(1)=alpha_(1)R.....(2)`
`alpha_(2)=alpha_(1)(2R)+alpha_(2)(R).......(3)`
For the block `ma=T_(1)......(4)`
For the spool `malpha_(1)=T_(2)-T_(1)-F.....(5)`
`((mR^(2))/2)alpha_(1)=T_(2)R+T_(1)R+fR.....(6)`
For the disc `ma_(2)=mg-T_(2)` .....(7)
`(1/2mR^(2))alpha^(2)=T_(2)R......(8)`
For these equations, we get `a=4/37 g`


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