Final answer:
The momentum of the bullet just before it hits the bag is 4kg·m/s. To stop the bullet, an average force of -363.64N was applied, which suggests the force acted opposite to the bullet's direction.
Step-by-step explanation:
The momentum of the bullet just before hitting the bag is calculated using the formula for momentum, which is the product of mass and velocity. The mass of the bullet is 20g (which is 0.02kg when converted to kilograms) and its velocity is 200m/s. So, the momentum (p) is:
p = mass × velocity = 0.02kg × 200m/s = 4kg·m/s.
To find the average force that stopped the bullet, we use the impulse-momentum theorem, which states that the change in momentum (impulse) is equal to the average force multiplied by the time the force is applied. Since the bullet comes to rest, its final momentum is 0kg·m/s, and the initial momentum is 4kg·m/s. The change in momentum is therefore -4kg·m/s (negative because the bullet is stopping).
Average force = Change in momentum / Time = -4kg·m/s / 0.011s = -363.64N.
The negative sign indicates that the force is in the opposite direction of the bullet's initial motion.