Fire!
A box with a mass of 248 g containing a very thick gel is placed, motionless, on a frictionless surface. A bullet with a mass of 2 g is fired at a speed of 1,250 m/s. The bullet embeds itself in the gel.
How fast will the box move across the frictionless surface, carrying the embedded bullet? Give answer in m/s.
The answer is 10.
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1 solution
Moderator note:
Simple standard approach using the conversation of linear momentum.
Why can't we say that the kinetic energy is constant?
The bullet has a total momentum of 2 * 1,250 = 2500
The total system of box + bullet has to have the same momentum after the bullet embeds itself in the gel. The mass of the system is 2 + 248 = 250
So the speed is 2,500/250 = 10 m/s