Collision of a stationary ball with a moving ball

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Homework Help Overview

The problem involves a collision between two identical balls, one moving and the other stationary. The first ball, referred to as "M," has an initial velocity represented by the vector 3i + 4j, while the second ball, "S," is stationary. After the collision, ball "M" moves in the direction of 3i + 16j, and ball "S" moves in the direction of i. The task is to demonstrate that this scenario can occur regardless of the initial speed of ball "M."

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the conservation of momentum and the law of restitution. The original poster attempts to set up equations based on these principles but expresses uncertainty about the next steps. Others inquire about resolving the equations to express final velocities in terms of the initial velocity scalar.

Discussion Status

The discussion is ongoing, with participants exploring the implications of the derived equations. Some guidance has been offered regarding the relationships between the variables, but there is no explicit consensus on the next steps or the overall resolution of the problem.

Contextual Notes

Participants are working within the constraints of the problem statement and the rules of momentum conservation. There is an emphasis on understanding the implications of the derived equations without reaching a definitive conclusion.

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Homework Statement



Two identical balls (same mass and material) , of which the first one (named ball "M") moving in the direction = 3i + 4j collides with the second ball (named ball "S") which is stationary. After the impact, the ball "M" moves in the direction= 3i + 16j while ball "S"
moves in the direction = i.

Show that this can happen whatever the initial speed of "M" .

Homework Equations



P(after impact) = P(before impact) (where P denotes the vector quantity momentum)

law of restitution.

The Attempt at a Solution



U shows Initial velocity

let U(of M) be = n( 3i + 4j ) [where n= any "scalar" ,thus showing initial velocity]
let U(of S) be = k (oi+0j) = 0

V shows final velocity

let V(of M) be = c( 3i + 16j ) [again "c" is a scalar]
let V(of S) be = d( i ) [because the impulse and force act horizontally]


The velocity in j direction remains constant, while momentum is conserved in the x direction.

so i got two equations :
1) 3n = 3c + d [from conservation of momentum in i direction]
2) 4n = 16c ⇔ n/c = 4 [velocity remains unchanged in j direction]

I don't know what to do next, how do i prove this ?
 
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Can you resolve the equations to obtain c and d expressed in terms of n? If yes, what does that mean?
 
voko said:
Can you resolve the equations to obtain c and d expressed in terms of n? If yes, what does that mean?

Certainly,

c=n/4

and d= 9n/4

It means that for any value of "n" there is a value of "c" and "d" .

I don't see how this helps me .
 
That proves what you are supposed to prove.
 

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