- #1

Valenti

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## Homework Statement

A red and a blue rubber puck are free to slide along a frictionless air table. Each has a mass of 40 grams. They collide in an elastic collision. Initially the red one is at rest and the blue one is traveling in the x direction with a speed of 4 m/s. After the collision the blue one is traveling in the direction +30 degrees, with the red one traveling in the direction ‐55 degrees. Using conservation of energy and momentum find the speed of each puck after the collision.

## Homework Equations

m1v1i+m2v2i = m1v1f + m2v2f

## The Attempt at a Solution

Really not too sure about this question so my answer may be way off

Solve for the momentum in each direction

m1v1i+m2v2i = m1v1f + m2v2f

X Direction

m1v1i+m2v2i = m1v1f + m2v2f

0.04kg(4m/s) + 0.04kg(0m/s) = 0.04 (v1f cos30) + 0.04(v2f cos-55)

0.16kgm/s = 0.03v1f + 0.02v2f

Y Direction

m1v1i+m2v2i = m1v1f + m2v2f

0.04kg(0) + 0.04kg(0m/s) = 0.04kg(v1f sin30) + 0.04kg (v2f sin-55)

0 = 0.02v1f - 0.03 v2f

Solve for one of the Velocities

0 = 0.02v1f - 0.03 v2f

0.03v2f = 0.02v1f

v2f = 2/3 v1f

Replace with new velocity

0.16kgm/s = 0.03v1f + 0.02v2f

0.16kgm/s = 0.03v1f + 0.02(2/3)v1f

0.16kgm/s = 0.03v1f + 1/75 v1f

0.16kgm/s = 13/300 v1f

3.69m/s = v1f

Solve for v2f

v2f = 2/3 v1f

v2f = 2/3 (3.69 m/s)

v2f = 2.46 m/s