In a ballistics test, a 25 g bullet traveling horizontally at 1200m/s goes throu
ID: 1724826 • Letter: I
Question
In a ballistics test, a 25 g bullet traveling horizontally at 1200m/s goes through a 30 cm thick 350 kgstationary target and emerges with a speed of 900 m/s. The target is free to slide on a smoothhorizontal surface. (a) How long is the bullet in the target?1 s
What average force does it exert on the target?
2 N (magnitudeonly)
(b) What is the target's speed just after the bullet emerges?
3 m/s (a) How long is the bullet in the target?
1 s
What average force does it exert on the target?
2 N (magnitudeonly)
(b) What is the target's speed just after the bullet emerges?
3 m/s
Explanation / Answer
Mass of the bullet m = 25 g = 0.025kgInitial velocity of th ebullet u = 1200 m/s Thickness of th etarget S = 30 cm = 0.3 m Mass of target M = 350 kg Initial velocity of th etarget U = 0 Velocity of the bullet after emerges from target v= 900 m/s (a) From the relation v ^ 2 - u ^ 2 = 2aS accleration a = [ v ^ 2 - u ^ 2 ] / 2S = -1050000 m / s ^2 from the relation required time t = ( v - u ) / a = 2.857 * 10 ^ -4 s
(b). from law of conservation of momentum , mu + MU = mv +MV 30 + 0 = 22.5 + 350 V from this velcoity of the target after colliison V =0.02142 m / s Average force does it exert on the target F = MV / t = 2.625 * 10 ^ 4 N
(b) the target's speed just after the bullet emerges V =0.02142 m / s