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Hey guys! I have this problem for an online homework assignment and I just can't get it right. My teacher never covered it in class and our textbook only covered it when the two colliding objects were the same weight. I would really appreciate some help!

A(n) 1.9 kg object moving at a speed of 4.9 m/s strikes a(n) 1.4 kg object initially at rest. Immediately after the collision, the 1.9 kg object has a velocity of 1.2 m/s directed 41° from its initial line of motion. What is the speed of the 1.4 kg object immediately after the collision? Answer in units of m/s.

m

v

These are the equations he wants us to use. He doesn't like us using equations he doesn't give us in class so any way to solve this problem using only them would be great. The problem doesn't say the collision is elastic though so I don't understand why they still apply.

Using the first equation I plugged in all the known information and got 5.02 m/s while the second gave me 6.1 m/s. Obviously something isn't right here. I also tried solving the problem using conservation of KE. I found all the KE for both objects in the x and y direction before and after the collision. Using the conservation principle I was able to solve for the KE of the second object in both the x and y direction. Because I have the mass of the object I was able to get the v in the x and y directions and I used the Pythagorean Theorem to solve for the overall v

Thanks!

## Homework Statement

A(n) 1.9 kg object moving at a speed of 4.9 m/s strikes a(n) 1.4 kg object initially at rest. Immediately after the collision, the 1.9 kg object has a velocity of 1.2 m/s directed 41° from its initial line of motion. What is the speed of the 1.4 kg object immediately after the collision? Answer in units of m/s.

## Homework Equations

m

_{1}(v_{i1}- v_{f1}) = m_{2}(v_{f2}- v_{i2})v

_{i1}+ v_{f1}= v_{f2}+ v_{i2}These are the equations he wants us to use. He doesn't like us using equations he doesn't give us in class so any way to solve this problem using only them would be great. The problem doesn't say the collision is elastic though so I don't understand why they still apply.

## The Attempt at a Solution

Using the first equation I plugged in all the known information and got 5.02 m/s while the second gave me 6.1 m/s. Obviously something isn't right here. I also tried solving the problem using conservation of KE. I found all the KE for both objects in the x and y direction before and after the collision. Using the conservation principle I was able to solve for the KE of the second object in both the x and y direction. Because I have the mass of the object I was able to get the v in the x and y directions and I used the Pythagorean Theorem to solve for the overall v

_{f}of the second object but that was wrong too. I'm not sure what to try next so please help me!Thanks!

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