• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4
5. 5
5
6. 6
6
7. 7
7
8. 8
8
9. 9
9
10. 10
10
11. 11
11
12. 12
12

# Force of friction

Extracts from this document...

Introduction

Kwun Tong Government Secondary School

Experiment Report

Experiment No.:              1

## Title:                      Force of friction

Date of Experiment:           2006/10/31

Mark:

 Sch. Code 2114 TAS Group 15 Name: Chan Man Lok Class: S.6C Class No.: 16

Objective:

1. To study the effects of the normal force, and surface area on the force of friction using a block.
2. To estimate the coefficients of static and kinetic friction.

Apparatus:

## Instrument

### Description

Wooden block

x 4

200g x 4

Spring balance

x 1

DCS/PL/2-2

0 - 10N

The smallest division = 0.2 N

Tripe beam balance

x 1

0 – 500g

The smallest division = 0.1g

Frictional paper

x 1

/

Rubber band

Several

/

Theory:

Limiting static friction :

Friction always opposes motion. Larger forces tending to produce the motion, larger friction is. However, it cannot increase indefinitely.

For example, when a body is in contact with a rough surface frictional forces arise at the contact surface if the body is subjected to an applied force. When the applied force exceeds the limiting static friction , the body will start to slip over the rough surface. And the value of  is roughly proportional to the normal force R.

where is the coefficient of static friction at maximum at the contact surface.

Kinetic friction :

However, the friction acting on a resting block is less than until the block starts to move. For example, once the body starts to move over the rough surface, the friction would decrease slightly to a value known as kinetic friction . So  is slightly less than  but it is still approximately proportional to R.

where

Middle

Assumption:

1. The spring balance was kept in horizontal position.
2. The rubber bands had no mass.
3. The gravitational acceleration is .
4. The blocks were pulled to move at a constant speed.

Result:

1. Frictional force and applied force

The 5 readings of spring balance which represent .

 /N 2 1.9 1.8 2 2.1

The mean of : N

The 5 readings of spring balance which represent .

 /N 1.3 1.4 1.5 1.4 1.3

The mean of : N

Graph of frictional force against the applied force

1. ##### Coefficients of friction for wooden blocks
 Number of blocks 1 2 3 4 Applied force F /N Limiting static friction 1.96 3 5.4 7.3 Kinetic friction 1.38 2.4 3.4 5.2 Normal force R / N 1.96 3.92 5.89 7.89
##### Graph of the limiting static friction against the normal force R

= slope,  = y-intercept

Graph of the limiting static friction against the normal force R

Take the maximum difference of the slopes and y-intercepts as the uncertainly.

Maximum uncertainty in slope

Maximum uncertainty in slope

Thus, slope

y-intercept

Conclusion

If the spring balance were not kept in horizontal position, the pulling force would be larger than the horizontal force. And make the results inaccurate. As a result, it was important to keep the pulling force in horizontal position.

Let pulling force be F, horizontal force be x

1. Mass of the rubber bands

The rubber bands used to keep the wooden blocks side by side had their own mass. So the normal force R didn’t only involved the weight of the blocks but also the weight of the rubber bands. It would affect the results if the mass of the rubber band were neglected. To improve the accuracy, the weight of the rubber bands should be measured and involved in R too.

1. Taking readings of the spring balance

In step A3, B6, C12, readings of the spring balance were taken during the blocks were moving at a constant speed. The difficulty was to take the readings in that instantaneous motion. It was easy to take inaccurate reading and hence affect the data. The only way to improve was doing the procedure repeatedly by several people and then taking the average of the readings.

Conclusion:

Through the experiment, the coefficient of static friction was found to be . The coefficient of kinetic friction was found to be .  is smaller than , so less force is needed to keep the block moving than to start moving it. Both limiting friction and kinetic friction were directly proportional to the normal reaction but are independent of the surface areas of the contact surface.

S.6 Physics TAS Experiment 1            Chan Man Lok 6C (16)              P.

This student written piece of work is one of many that can be found in our AS and A Level Fields & Forces section.

## Found what you're looking for?

• Start learning 29% faster today
• 150,000+ documents available
• Just £6.99 a month

Not the one? Search for your essay title...
• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month

# Related AS and A Level Fields & Forces essays

1. ## Investigating the forces acting on a trolley on a ramp

5 star(s)

Thus, because in this experiment u was 0, the resulting rearranged formula was; a = v2 / 2s Hence, it was possible to find the acceleration along the slope by taking the gradient of the resulting regression lines plotted through the data.

2. ## The experiment involves the determination, of the effective mass of a spring (ms) and ...

0.025 diff = 0.075 diff2 = 0.14 - 0.025 diff2 = 0.115 The average of these two values is then found, av = 0.115 + 0.075 2 av = 0.095 kg This is the uncurtainty in ms so it can now be said that, ms = 0.025 +/?

1. ## Experiment to determine gravity from a spring using analogue techniques

a value for g can be calculated from this graph and the spring constant calculated previously: Uncertainties Calculating Uncertainty in g To calculate the uncertainty in g, the same method used for spring 1 is used. Using LINEST, the value for the gradient is: This is combined for the uncertainty in g.

2. ## Experiment test for F = m2L by whirling a rubber bung (centripetal force)

?� � T� & T cos ? = mg ? T�(M�) � cos ?v � ?� ? If kept L & m constant & increase ?, M was required to increase. 6. ? Mg = m?2L ? If we want to increase the angular velocity ?

1. ## Sliding &amp;amp; Friction Lab Report

65 ms 120.8g 1,208 N Granite 4 small washers 48 ms 60.4g 604 N Styrofoam 6 small washers 47 ms 90.6g 906 N IV. Conclusion Shannon and I did answer our question. We thought different surface areas would affect the force of friction, and it did.

2. ## Does the mass of a block of wood effect the size of a frictional ...

I predict that the frictional force exerted on the block with different masses on top of the block will be directly proportional.

1. ## Investigating the relationship of projectile range and projectile motion using a ski jump.

I believe this is the reason that the line on the graph isn't directly proportional to the x and y components. Therefore in the absence of air resistance, I believe that the graph produced would be directly proportional to both x and y components.

2. ## Einstein's theory of relativity.

The result in both cases will be the same. From this principle, Einstein reasoned that matter in space distorts or "curves" the frame of reference of space. The result of this curvature is what we experience as gravity. Euclidian or "flat" geometry cannot describe curved space.

• Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to