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A bullet of mass 200 g hits a block of thickness 6 cm with a speed of `100ms^(-1).` It emerges with `10%` of its initial KE. Find its emergent speed

Answer» `K_(i)"initial"KE=1/2mu^(2)" "m=200/1000kg" "u=100ms^(-1)" ""Final"KE=0.1K_(i)=1/2mv^(2)`
`K_(i)` initial `KE=1/2m u ^(2)=1/2xx(200)/(1000)xx100xx100=1000J`
`K_(f)="final" KE=0.1xxK_(i)=0.1xx1000=100J`
`1/2mv^(2)=100`
`v=sqrt(((2xx100)/(200))/(1000))=10sqrt10=31.6ms^(-1)`
Speed is redued by `68%` (not98%`).


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