# Momentum question?

2 carts both 3kg and 1.2 kg are moving at 2.5m/s and 1.8m/s respectively, these 2 carts move directly at each other and collide, the 2 carts sticks together after the collision, find the velocity of the system post collision.

### 3 Answers

- electron1Lv 76 months ago
For cart #1, initial momentum = 3 * 2.5 = 7.5 kg * m/s

Since the second cart is moving toward the first cart, its initial velocity is negative.

For the second cart, initial momentum = 1.2 * -1.8 = -2.16 kg * m/s

Total initial momentum = 7.5 – 2.16 = 5.34 kg * m/s

Total mass = 3 + 1.2 = 4.2 kg

Final momentum = 4.2 * v

4.2 * v = 5.34

v = 5.34 ÷ 4.2

This is approximately 1.3 m/s. I hope this is helpful for you.

- oldschoolLv 76 months ago
Vector momentum before = vector momentum after:

3*2.5 -1.2*1.8 = 7.5 - 2.16 = 5.34kg•m/s

5.34 = (3+1.2)V ------> 5.34/(3+1.2) = V = 1.27 or ≈ 1.3m/s <<<<<