- #1

Kennedy111

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**Energy Question! Please Help!**

## Homework Statement

A 170g hockey puck sliding at 25 m/s slows to a speed of 10 m/s in a distance of 7.5m. Determine the force of friction causing the puck to slow down.

m=170g

= 0.170kg

V1 = 25 m/s

V2= 10 m/s

d = 7.5 m/s

## Homework Equations

Kinetic Energy = (1/2)(m)(v^2)

Work = Fd

## The Attempt at a Solution

I'm really confused...

Kinetic Energy 1 = (1/2)(0.170kg)(25m/s)

= 2.125 J

Kinetic Energy 2 = (1/2)(0.170kg)(10m/s)

= 0.85 J

Kinetic Energy 2 - Kinetic Energy 1

0.85 J - 2.125 J = -1.325 J

Work = Fd

F = Work/d

= -1.325/7.5m

= -0.176666... which is wrong!

Please help!