(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

a hockey player of mass 80 kg was skating at a velocity of 7.5 m/s [E 20 S] when he accidently hit a linesman who was just standing on the ice. The mass of the linesmass is 90 kg and his velocity after the collision was 3 m/s [E 30 N] find.

a) the velocity of the hockey player after the collision and

b) the kinetic energy lost during the collision as a percentage.

3. The attempt at a solution

given:

m1= 80 kg

m2 = 90 kg

v1 = 7.5 m/s [ E 20 S]

v1` = ?

v2= 0m/s

v2` = 3m/s [ E 30 N]

X component

m1v1 = m1v1` + m2m2`

(80kg)(7.047694656m/s[E]) = (80kg)(v1`) + (90kg)(2.598076211[E])

563.8155725 kgm/s [E] - 233.826859 kgm/s[E] = (80kg)(v1`)

329.9887135 [E] / 80kg = v1`

4.124858919 m/s [E] = v1`

y components

m1v1 = m1v1` + m2v2`

(80kg)(2.565151075m/s) = (80kg)(v1`) + (90kg)(1.5m/s[N])

205.212086kgm/s-135m/s[N] = (80kg)(v1`)

70.212086kgm/s/80kg = v1`

4.252651075m/s = v1`

4.124858919 m/s [E] + 4.252651075m/s = v1`

5.924 m/s [S 44° E] = v1`

b) Ektot = 1/2m1v1^2

Ektot= 1/2(80kg)(7.5m/s)^2

Ektot=2250 J

Ektot` = 1/2m1v1`^2 + 1/2m2v2`

Ektot` = 1/2(80kg)(5.924m/s)^2 + 1/2(90kg)(3m/s)^2

Ektot` =1403.75104 J + 405 kg J

Ektot` = 1808.75104 J

Ektot - Wdef = Ektot`

2250 J - Wdef = 1808.75104 J

Wdef = 441.24896 J

The Wdef is the energy lost during the collision

(441.248896 J / 2250 J) x 100%

19.6 %

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# Homework Help: Kinetic energy along with conservation of momentum

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