# Homework Help: Projectile collision

1. Oct 30, 2006

### kbyws37

A projectile of mass 1.9 kg approaches a stationary target body at 4.8 m/s. The projectile is deflected through an angle of 59.6° and its speed after the collision is 3.0 m/s. What is the magnitude of the momentum of the target body after the collision?

Here momentum is conserved so Pi = Pf

3m/s*1.9kg*sin(59.6) = 4.92
3m/s*1.9kg*cos(59.6) = 2.88

i plugged it into
M1V1i + M2V2i = M1V1f + M2V2f
(1.9)(4.8) + M2V2i = 4.92 + 2.88
9.12 + M2V2i = 7.8
M2V2i = 1.32

however, my answer is wrong and i think it's b/c i plugged in numbers incorrectly.

2. Oct 30, 2006

### OlderDan

You need to keep your "1"s and "2"s and your "i"s and "f"s straight. You should have 2 equations. One for the direction the projectile was moving before collision, and one for the perpendicular direction.

3. Oct 30, 2006

### kbyws37

Before collision
m1v1 = (1.9)(4.8) = 9.12

After collision
3m/s*1.9kg*sin(59.6) = 4.92
which is in the perpendicular direction

i'm not quite sure what to do next

4. Oct 30, 2006

### OlderDan

The sum of the momentum components perpendicular to the initial momentum must be zero. The sum of the momentum components parallel to the initial momentum must equal the initial momentum. Write the momentim components for the target in terms of an unknown angle, and write two equations, one for the sum of the parallel components and one for the sum of the perpendicular components.