1.

Hammer of mass M strikes a nail of mass’m’ with a velocity 20 m//s into a fixed wall. The nail penetrates into the wall to a depth of 1 cm. The average resistance of the wall to the penetration of the nail is

Answer»

`((M^(2))/(M+m))xx10^(3)`
`((2M^(2))/(M+m))xx10^(4)`
`((M)/(M^(2)))xx10^(2)`
`((M^(2))/(M+m))xx10^(2)`

Solution :From conservation of momentum
`MV+ m (0) = (M+ m) V^(1)`
`V = 20 m//s`
From WORK Energy theorem, `1/2 (M+ m) V^(2)= f xx 1cm`
`f=1/2 (M+ m)((Mxx20)/(M+m))^(2)`
`f=(2M^(2))/(M+m)xx!)^(4)N`


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