A 2.0-kg pistol fires a 1.0-g bullet with a muzzle speed of 1000 m/s. The bullet then strikes a 10-kg wooden block resting on a horizontal frictionless surface. The block and the embedded bullet then slide across the surface.
-What is the speed of the "bullet + block" system immediately after the bullet is embedded in the block?
A)0.1 m/s
B)10 m/s
C)1000 m/s
D)10 000 m/s
E)zero m/s

Question

A 2.0-kg pistol fires a 1.0-g bullet with a muzzle speed of 1000 m/s. The bullet then strikes a 10-kg wooden block resting on a horizontal frictionless surface. The block and the embedded bullet then slide across the surface. 
-What is the speed of the "bullet + block" system immediately after the bullet is embedded in the block?
A)0.1 m/s 
B)10 m/s 
C)1000 m/s 
D)10 000 m/s 
E)zero m/s

Quizplus · Accepted Answer

The speed of the "bullet + block" system immediately after the bullet is embedded in the block is determined by the conservation of momentum. If the bullet is initially moving and the block is stationary, the combined system will have a speed that is less than the initial speed of the bullet, typically much lower than the bullet's initial speed, making 0.1 m/s a plausible answer.

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