1.

A shell of mass `4kg` moving with a velocoity `10m//s` vertically upward explodes into three parts at a height `50m` from ground. After three seconds, one part of mass `2kg` reaches ground and another part of mass `1kg` is at height `40m` from ground. The height of the third part from the ground is : `[g=10m//s^(2)]`A. `50m`B. `80m`C. `100m`D. none of these

Answer» Correct Answer - C
After `3 sec.` height of `COM. ` is `50+ut-(1)/(2) g t^(2)`
`= 50+10xx3-(1)/(2)xx10xx3^(2)`
`=35m`
`H_(C.M.) = (m_(1)H_(1)+m_(2)H_(2)+m_(3)H_(3))/(m_(1)+m_(2)+m_(3))`
`35=(2xx0+1xx40+1xxH_(3))/(4)`
`H_(3)=100m`


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