1. punchthis22
Ina shoots a large marble (Marble A, mass: 0.08 kg) at a smaller marble (Marble B, mass: 0.05 kg) that is sitting still. Marble A was initially moving at a velocity of 0.5 m/s, but after the collision it has a velocity of –0.1 m/s. What is the resulting velocity of marble B after the collision? Be sure to show your work for solving this problem along with the final answer.
There seems to be something wrong here.
Using conservation of linear momentum with the numbers given, I can work out a resulting velocity for v. BUT ... To check it, I’ve tried to apply conservation of kinetic energy, or at least COMPARE the kinetic energies before and after collision.
Before
After
According to this, there’s MORE kinetic energy AFTER the collision than before. Which should be nonsense ?

2. Before B A
Momentum
Total momentum before collision
After B A
Momentum
Total momentum after collision

3. Total momentum before collision
Total momentum after collision B A B A
The smaller mass gets a big kick from the larger mass. (Hence maybe the expression “pick on someone your own size”.)

4. Total kinetic energy before collision
Total kinetic energy after collision
According to this, there’s MORE kinetic energy AFTER the collision than before. Which should be nonsense ?