Speeds of tennis balls after collision

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Homework Help Overview

The problem involves a head-on collision between two tennis balls of different masses, specifically focusing on the speeds and directions of the balls after a perfectly elastic collision. The subject area includes concepts from mechanics, particularly conservation of momentum and energy in collisions.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of conservation of momentum and the need for an additional equation related to the velocities after the collision. There is uncertainty about how to derive the final velocities and the number of variables involved in the equations.

Discussion Status

The discussion is ongoing, with participants attempting to clarify the equations needed for the problem. Some have offered guidance on using elimination or substitution methods, while others express confusion about the number of variables and the setup of the equations.

Contextual Notes

Participants are navigating the constraints of the problem, including the requirement for a perfectly elastic collision and the implications of mass remaining constant. There is also a mention of potential mistakes in earlier calculations that could affect their approach.

balletgirl
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Homework Statement



A 0.0600 kg tennis ball, moving with a speed of 2.50 m/s, has a head-on collision with a 0.0900 kg ball initially moving away from it at a speed of 1.00 m/s. Assuming a perfectly elastic collision, what is the speed and direction of each ball after the collision?

Homework Equations



m1v1+m2v2 = m1v1'+m2v2'

The Attempt at a Solution



with the given, I know that
m1= .06 kg
m2=.09 kg
v1= 2.5 m/s
v2= 1.0 m/s
after this, I don't know where to start?
 
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Hi balletgirl

Plug all the data to the equation you wrote and you lack one more equation, which is V1-V2=V2' - V1'
 
Okay so I do 2.5-1.0= V2'-V1'. I don't understand how you find those final numbers.
&
.06kg(2.5m/s) + (.09kg)(1.0m/s) = m1v1'+m2v2'
 
You have two equations and two variables so just use elimination or substitution
 
I don't understand the concept.
I thought I was solving for four variables: m1' v1' m2' and v2'
Anyways I got to .135=m1v1'+m2v2'
1.5= V2'-V1'

it didn't work out when I tried using elimination or substitution
 
Okay just realized a dumb mistake. The mass will stay the same. This will make everything a lot easier for me.
 

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