49.5k views
1 vote
A 2.0 kilogram rifle initially at rest fires a 0.002 kilogram bullet. As the bullet leaves the rifle with a velocity of 500 meters per second , what is the momentum of the rifle -bullet system ?

User Earlz
by
3.9k points

1 Answer

1 vote

Final answer:

The momentum of the rifle-bullet system remains constant and is initially zero. When the bullet is fired, it acquires a momentum of 1 kg·m/s while the rifle acquires an equal and opposite momentum of -1 kg·m/s, preserving the system's total momentum.

Step-by-step explanation:

The student is asking about the momentum of a rifle-bullet system using the concept of conservation of momentum in Physics. The law of conservation of momentum states that the momentum of an isolated system remains constant if no external forces act upon it. In the case of a rifle firing a bullet, the bullet gains forward momentum, and the rifle gains an equal amount of backward momentum.

To find the momentum of the rifle-bullet system, we apply the formula for momentum (p) which is the product of mass (m) and velocity (v): p = m × v. Since the rifle is initially at rest, its initial momentum is zero. When the bullet is fired with a velocity of 500 meters per second (m/s), its momentum would be:
p_{bullet} = m_{bullet} × v_{bullet} = 0.002 kg × 500 m/s = 1 kg·m/s.

By the conservation of momentum, the momentum of the rifle must be equal and opposite to that of the bullet. Therefore, the momentum of the rifle is -1 kg·m/s. Notice the negative sign, which indicates that the rifle's momentum is in the opposite direction to the bullet's momentum. Since they are equal in magnitude but opposite in direction, the total momentum of the rifle-bullet system is zero, as it was initially.

User Dahlbyk
by
4.0k points