Question

A 5000-kg freight car crashes into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg freight car? A 5000-kg freight car crashes into a 10,000-kg freight car at rest. They couple upon collision and move with a speed of 2 m/s. What was the initial speed of the 5000-kg freight car? a) 4 m/s b) 8 m/s c) 6 m/s d) 5 m/s e) none of the above

Answer 1

Answer:

$v_{1i} = 6 m/s$

Explanation:

Here we know that the whole system is having no external force on it

So the total momentum of the system will remain conserved

So here we can say

$m_1v_{1i} + m_2v_{2i} = (m_1 + m_2) v_f$

here we have

$m_1 = 5000 kg$

$m_2 = 10,000 kg$

$v_{2i} = 0$

$v_f = 2 m/s$

now we have

$5000(v_{1i}) + 0 = (5000 + 10000) (2)$

$v_i = \frac{15000}{5000}(2)$

$v_{1i} = 6 m/s$