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 B) 2000 C) 3000 D) 5000

Question

Quizplus · Accepted Answer

Using the principle of conservation of momentum, we can solve for the number of bullets:
m_car * V_car = m_bullet * V_bullet
where m_car and V_car represent the mass and velocity of the railroad car respectively, and m_bullet and V_bullet represent the mass and velocity of each bullet. 
Rearranging the equation, we get:
m_bullet = m_car * V_car / V_bullet
Substituting the given values, we get:
m_bullet = (6.25 × 10¹⁴ kg) * (0.3 m/s) / (0.025 kg * 250 m/s) 
m_bullet = 3,000
Therefore, 3,000 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. 
Hence, the answer is C.

A Machine Gun Is Attached to a Railroad Flatcar That