- #1

mybrohshi5

- 365

- 0

## Homework Statement

Hockey puck B rests on a smooth ice surface and is struck by a second puck A, which has the same mass. Puck A is initially traveling at 15.2 m/s and is deflected 30.0^\circ from its initial direction. The pucks are made of superball-like material, so you may assume that the collision is perfectly elastic.

**Find the final speed of the puck A after the collision**

## Homework Equations

conservation of momentum for one object at rest (1)

mv

_{ai}= mv

_{af}+ mv

_{bf}

conservation of kinetic energy (2)

1/2mv

_{ai}= 1/2mv

_{af}+ 1/2mv

_{bf}

## The Attempt at a Solution

I have tried this about 10 times and cannot get it right :(

i solved equation 1 for the x and y components of the velocity final for puck b

v

_{bxf}= v

_{axi}- v

_{axf}

v

_{byf}= -v

_{ayf}

so

v

_{bf}= sqrt [(v

_{axi}- v

_{axf})

^{2}+ (-v

_{ayf})

^{2}]

v

_{bf}= sqrt [v

_{axi}

^{2}- 2v

_{axf}+ v

_{axf}

^{2}+ v

_{ayf}

^{2}]

then i plugged this into 1/2mv

_{ai}= 1/2mv

_{af}+ 1/2mv

_{bf}for v_bf

i would show all my steps of reducing but it would take forever.

i end up getting v

_{fa}= cos(30) = .866 but this is wrong

am i right up to this point of what i have done?

any help would be great. Thank you