Initial Velocity, Equal Mass Collision: Angle Calculation

[SJEllmann]

After a completely inelastic collision between two objects of equal mass, each hacing initial speed v, the two move off together with speed v/3. What was the angle between their initial directions?

 

[Doc Al]

Where did you get stuck?

 

[SJEllmann]

i don't know where to begin, i hate the problems that just give you variables.

 

[Doc Al]

Begin by drawing a diagram. Have one object move along the x-axis; the other move at some angle theta to the x-axis. Apply conservation of momentum and you'll be able to solve for theta.

 

[wysard]

Dang Doc! I understand that, but you want to bet the OP doesn't?

Besides, the collision is inelastic. Do we not need to know the coefficient of elasticity so we can determine how much of the energy is transferred back to the new "v" as opposed to lost in heat or other phenomena that is part of inelasticity?

 

[Doc Al]

Dang Doc! I understand that, but you want to bet the OP doesn't?

One step at a time.

Besides, the collision is inelastic. Do we not need to know the coefficient of elasticity so we can determine how much of the energy is transferred back to the new "v" as opposed to lost in heat or other phenomena that is part of inelasticity?

No need for such heavy artillery. The collision is completely inelastic: The two objects stick together after the collision. That's all you need to know.

 

[SJEllmann]

thanks i think i got it, can someone work it out to see if they get 45 degrees as the angle?

 

[Doc Al]

thanks i think i got it, can someone work it out to see if they get 45 degrees as the angle?

No, that's not right. Show exactly what you did.