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

[jon_i]

A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25  104 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. 400
  c. 3000
  b. 2000
  d. 5000

Question 2

A proton (+1.6  10-19 C) moves 10 cm on a path in the direction opposite to a uniform electric field of strength 3.0 N/C. How much work is done on the proton by the electrical field?
 a. 4.8  10-20 J
  c. zero
  b. 1.6  10-20 J
  d. -4.8  10-20 J

[joshbk44]

Answer to Question 1

C

Answer to Question 2

D