In a ballistics test, a 20.0g bullet traveling horizontally at 1100m/s goes thro
ID: 2186072 • Letter: I
Question
In a ballistics test, a 20.0g bullet traveling horizontally at 1100m/s goes through a 40.0cm -thick 450kg stationary target and emerges with a speed of 900m/s . The target is free to slide on a smooth horizontal surface. How long is the bullet in the target? What average force does the bullet exert on the target? What is the target's speed just after the bullet emerges?Explanation / Answer
m=20g vi=1100m/s d=.4m m=450kg vf=900m/s momentum conservation inital p=.02*1100 final p=.02*900+450*v =>inital p=final p =>900*.02+450v=.02*1100 =>v=.02*200/450=8.89*10^-3 m/s v-u=at -1100+900=a*t =>-200=at v^2-u^2=2as 900^2-1100^2=2*a*.4 =>a=-5*10^5m/s^2 t=-200/-5*10^5=.4ms F =mv/t=450*8.89*10^-3/.4*10^-3 =10KN