# Frictional Forces-finding velocity and distance

• gungo
In summary, a 0.170 kg hockey puck initially moving at 21.2 m/s [W] along the ice experiences a coefficient of kinetic friction of 0.005. After traveling 58.5 m, the puck's speed is 21.1 m/s. When the ice becomes rougher and the coefficient of kinetic friction increases to 0.047, the puck travels 6.24 m with the same initial and final speeds.
gungo

## Homework Statement

A 0.170 kg hockey puck is initially moving at 21.2 m/s [W] along the ice. The coefficient
of kinetic friction for the puck and the ice is 0.005.

(a) What is the speed of the puck after traveling 58.5 m?
(b) After being played on for a while, the ice becomes rougher and the coefficient of
kinetic friction increases to 0.047. How far will the puck travel if its initial and final
speeds are the same as before?

Fnet=ma
Ff=μkFn

## The Attempt at a Solution

a) FN=9.8(0.170)=1.666
Ff=0.005(1.6660)=0.00833
Fnet=ma
0.00833=0.170a =0.049
v2^2=(21.2)^2+2(0.049)(58.5)
v2=21.3, but the answer is 21.1

b)Ff=0.047(1.666)
Ff=0.078302
0.078302=0.170a=0.4606
I'll use the correct v2
21.1^2=21.2^2+2(0.4606)d
-4.23=0.9212d
d=-4.59 but the answer is 6.24
Not sure where I'm going wrong?

Does friction acting on the puck produce a positive or negative acceleration?

TomHart said:
Does friction acting on the puck produce a positive or negative acceleration?
Negative, so v2^2=(21.2)^2+2(-0.049)(58.5), v2=21.1
21.1^2=21.2^2+2(-0.4606)d

-4.23=-0.9212d
d=4.59...
That helped fix my mistake in (a) but how about b?

For part b, you really should use more significant digits than 21.1. I think a more accurate number was 21.06. That should resolve that problem - I think.

TomHart said:
For part b, you really should use more significant digits than 21.1. I think a more accurate number was 21.06. That should resolve that problem - I think.
Oh wow that made a difference than you so much!

TomHart

## What is frictional force?

Frictional force is a resistive force that acts in the opposite direction of an object's motion. It is caused by the interaction between two surfaces in contact.

## How is frictional force calculated?

Frictional force can be calculated using the equation F = μN, where F is the frictional force, μ is the coefficient of friction, and N is the normal force.

## What factors affect frictional force?

The factors that affect frictional force include the roughness of the surfaces, the amount of force pushing the surfaces together, and the type of material the surfaces are made of.

## How can frictional force be reduced?

Frictional force can be reduced by using lubricants, such as oil or grease, between the surfaces, or by making the surfaces smoother.

## Can frictional force be completely eliminated?

No, frictional force cannot be completely eliminated. It is a natural force that occurs whenever there is contact between two surfaces. However, it can be minimized through various methods.

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