A bullet of mass 5gm is fired horizontally into block of mass 1kg at rest on a horizontal surface and gets embedded in it. The combination moves 5m before coming to rest. If mu_(k)=0.40, what is the speed with which the bullet strikes the block ?

A bullet of mass 5gm is fired horizontally into block of mass 1kg at r

1.	A bullet of mass 5gm is fired horizontally into block of mass 1kg at rest on a horizontal surface and gets embedded in it. The combination moves 5m before coming to rest. If mu_(k)=0.40, what is the speed with which the bullet strikes the block ?
Answer» Solution :Mass of bullet `=m=5gm=0.005kg` Mass of block `=M=1kg` `mu_(k)=0.4` DISTANCE travelled `=s=5m` The KINETIC energy of the bullet is used to do work against the force of FRICTION between the block and the horizontal surface `(1)/(2)mv^(2)=Fs=mu_(s)Ns` But `N=(m+M)g` `(1)/(2)mv(2)=mu_(4)(m+M)g` `v=sqrt((2mu_(g)(m+M)g)/(m))=sqrt(((2xx0.4xx1.005xx9.8))/(0.005))=39.7m//s`