It is well known that bullets and other missiles fired at Superman simply bounce off his chest. Suppose that a gangster sprays Superman's chest with 8 g bullets at the rate of 105 bullets/min, the speed of each bullet being 450 m/s. Suppose too that the bullets rebound straight back with no change in speed. What is the magnitude of the average force on Superman's chest from the stream of bullets?

mv = 2x(0.008kgx450m/s) = 7.2kgm/s

=105(7.2)/min = 756 (kgm/s)/(min x (60s/1min))

=12.6 N

To find the magnitude of the average force on Superman's chest from the stream of bullets, we can use the concept of momentum.

The momentum of an object is given by the product of its mass and velocity. In this case, since the bullets rebound straight back with no change in speed, the change in momentum of each bullet when it hits Superman is twice its initial momentum.

First, let's find the momentum of one bullet:
Momentum = mass × velocity

Given:
Mass of each bullet (m) = 8 g = 8 × 10^(-3) kg
Velocity of each bullet (v) = 450 m/s

Momentum of one bullet = (8 × 10^(-3)) kg × 450 m/s

Now, let's calculate the rate at which bullets are hitting Superman's chest:
Rate of bullets hitting (r) = 105 bullets/min

To convert the rate from minutes to seconds, we divide by 60:
Rate of bullets hitting in seconds (r') = (105 bullets/min) ÷ 60

Next, let's calculate the total momentum change per second:
Momentum change per second = (Momentum of one bullet) × (Rate of bullets hitting in seconds)

Finally, we can calculate the magnitude of the average force on Superman's chest using Newton's second law of motion which states that force (F) is equal to the rate of change of momentum (dp/dt):
Average force = Momentum change per second ÷ Time

The time (t) taken for the bullet to rebound depends on how quickly it rebounds, but without that information, we cannot calculate the average force accurately.