# Objective: The pu by HC121104002213

VIEWS: 0 PAGES: 2

• pg 1
```									Physics 3U                 Coefficient of Friction

Objective: The purpose of this experiment is to determine the coefficient of static
friction and the coefficient of kinetic friction between a block of wood and a wooden
plank

Apparatus:
Wooden block with hook                           Newton spring scale
Wooden plank                                     masses

Method:
1. While performing this experiment, record any additional observations that seem
relevant.
2. Use the spring scale to determine the weight of the block.
3. Place the block on the wooden plank.
4. Determine the maximum amount of force that can be exerted on the block before
it starts moving. This is equal to the maximum static friction force on the block.
Record this value.
5. Determine the force required to slowly move the block along the wooden plank.
This is equal to the force of kinetic friction on the block. Record this value.
6. Determine the weight of a mass using the spring scale, record this value, then
place the mass on the wooden block.
7. Repeat steps 4, 5, and 6 until you have at least 6 measurements each of static
and kinetic force for different weights.

Observations:

Any measurements and other observations should be noted in this section of the lab
write-up

Calculations/Analysis:
1. The total weight of the block and the masses for any given measurement is equal
to the normal force on the block.
2. Graph force of friction (vertical axis) versus normal force (horizontal axis) for
static friction.
3. Determine the slope of the best fit line for the above graph. This is the coefficient
of static friction.
4. Graph force of friction (vertical axis) versus normal force (horizontal axis) for
kinetic friction.
5. Determine the slope of the best fit line for the above graph. This is the coefficient
of kinetic friction.

Sources of Error:

When you make measurements, make a note of the possible measurement error. For
example, when measuring with a metre stick that has no divisions smaller than cm this
means that a measurement could be off by up to about 0.5 cm (e.g. a measurement of
23 cm might actually be 23.4 cm).
Physics 3U                       Coefficient of Friction

On your graph, you should show possible errors in your measurements using error bars.
To estimate error in slope, draw both the maximum possible and minimum possible
slopes that still go through all the error bars. Those two slopes are a reasonable range

For this lab, at minimum you should quantify the possible effect of errors in measuring
frictional force and errors in measuring normal force.

Conclusions:
State your calculated value of both coefficients of friction as well as the uncertainty in
that calculation because of measurement and other errors. A comparison with an
accepted value of those coefficients would be welcome.

Improvements:

Suggest any improvements to this lab which would make the lab easier, more efficient,
or more accurate.

In particular, suggest ways that would reduce the effects of the most serious
measurement error discussed above.

Rubric for Evaluation

Category/              Level 4 (do it with   Level 3              Level 2 (do more     Level 1 (do the
Criterion              high effectiveness)   (do it right)        than the obvious)    obvious)
Thinking/Investigat    Analyses and          Analyses and         Analyses and         Analyses and
ion                    interprets results    interprets results   interprets results   interprets results
- analyzing and        with a high degree    with considerable    with some            with limited
interpreting results   of effectiveness      of effectiveness     effectiveness        effectiveness
Communication –        expresses and         expresses and        expresses and        expresses and
expression and         organizes ideas       organizes ideas      organizes ideas      organizes ideas
organization of        and information       and information      and information      and information
ideas and              with a high           with considerable    with some            with limited
information            degree of             effectiveness        effectiveness        effectiveness
effectiveness
Application –          Applies dynamics      Applies dynamics     Applies dynamics     Applies dynamics
applies dynamics       knowledge with a      knowledge with       knowledge with       knowledge with
knowledge to lab       high degree of        considerable         some                 limited
effectiveness         effectiveness        effectiveness        effectiveness

***to save paper, please hand in this rubric with the lab***

```
To top