A machine gun is attached to a railroad flatcar that rolls with negligible frict

Question

A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25 times 10^4 kg, how many bullets of mass 25 g would have to be fired at 250 m/s off the back to give the railroad car a forward velocity of 0.3 m/s? A tennis ball is held above and in contact with a basketball, and then both are simultaneously dropped. The tennis ball bounces off the basketball at a fairly high speed. This is because: the basketball falls farther than the tennis ball. the tennis ball is slightly shielded from the Earth's gravitational pull. the massive basketball transfers momentum to the lighter tennis ball. the tennis ball has a smaller radius. *Alex throws a 0.43-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s, and just after is 5.5 m/s. What is the magnitude of the change in the ball's momentum? 0.09 kgmiddot* m/s 1.0 kg * m/s 4.3 kg * m/s 5.2 kg *middotm/s In a two-body collision, if the kinetic energy of the system is conserved, then which of the following best describes the momentum after the collision? must be less must also be conserved may also be conserved is doubled in value

Explanation / Answer

Question 6) Using conservation of momentum

M1*v1 = n*M2*v2

Given M1 = 6.25*10^4 kg , M2= 0.025 kg, v1= 0.3 m/s,v2 = 250m/s , n is the number of bullets

So,

n = M1*v1/M2*v2

n = 6.25*10^4*0.3/(0.025*250)

n = 3000

Therefore, number of bullets = 3000

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