Physics Question Help?

Question

A 1.6kg object moving at a speed of 8.9m/s strikes a 1.2 kg object intially at rest. Immediately after the collision, the 1.6kg object has a velocity of 1.3m/s directed 21 degrees from its intial line of motion. What is the speed of the 1.2kg object immediately after the collision. Answer in m/s.

Answer 1

In collisions, linear momentum is always conserved.

Since this is a two-dimensional problem, we need to conserve momentum on each axis.

Conservation of momentum, x axis

(1.6 kg)(8.9 m/s) + (1.2 kg)(0) = (1.6 kg)(1.3 m/s)(cos 21) + (1.2 kg)(vx)

There's only one unknown, vx; solve for it.

Conservation of momentum, y axis

0 + 0 = (1.5 kg)(1.3 m/s)(sin 21) + (1.2 kg)(vy)

Again, there's only one unknown; solve for vy.

Now you have the two components of the velocity of the 1.2 kg object. Combine them to find velocity and angle.