Calculate Force of Friction on Hockey Puck Slowing to 10m/s

[Kennedy111]

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!

 

[azizlwl]

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!

Check you equation.
v²

 

[Kennedy111]

Oh duh! That was dumb of me! Thank you so much!