• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Force of Friction experiment

Extracts from this document...

Introduction

AL Physics TAS 4 (A1) – FULL REPORTimage00.png

Force of Friction

(2008/12/17)

1. Objective

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

2. Apparatus

  • Wooden block (190.0 g) × 3
  • Elastic strings
  • Wooden plank × 1
  • Spring balance × 1
  • Plastic plate × 1
  • Balance × 1
  • Brick × 1

3. Theory

Limiting static friction image06.pngimage01.png

Friction always opposes motion. It increases with the applied force. However, it cannot increase indefinitely.

When a body is in contact with a rough surface, friction arises at the contact surface if the body is subjected to an applied force. When the applied force exceeds the limiting static friction image06.png, the body will start to slip over the rough surface. And the value of image06.png is roughly proportional to the normal reaction R.

image13.png where image10.pngis the coefficient of static friction at the contact surface.


Kinetic friction image09.png

Generally, the friction acting on a resting block is less than image06.pnguntil the block starts to move. Once the body starts to move over the rough surface, the friction would decrease slightly to a value known as kinetic friction image09.png. So image09.png is slightly less than image06.png but it is still approximately proportional to R.

image07.png where image08.pngis the coefficient of kinetic friction at the contact surface.image02.png

image09.png remains constant even the applied force is increased further.

image08.pngis slightly less than image10.png.

3. Procedure

A.

...read more.

Middle

Block sliding:

1

2

3

4

5

Reading / N

0.4

0.5

0.4

0.3

0.4

Therefore, for a wooden block on a wooden plank, the limiting static friction image06.png is 1.1 N.

image12.png

B.        Coefficients of friction for various materials

Wood on wooden plank:

Number of blocks

1

2

3

image06.png/ N

1.1

2.0

3.2

image09.png/ N

0.4

1.1

1.5

R / N

1.86

3.73

5.59

image03.png

Wood on plastic plate:

Number of blocks

1

2

3

image06.png/ N

0.9

1.6

2.3

image09.png/ N

0.3

0.8

1.1

R / N

1.86

3.73

5.59

image04.png

Wood on brick:

Number of blocks

1

2

3

image06.png/ N

2.2

4.6

6.5

image09.png/ N

1.2

2.2

3.4

R / N

1.86

3.73

5.59

image05.png

The coeffiient of friction of the wooden blocks on various materials are summarized as follow:

wooden plank

plastic plate

brick

image10.png

0.57

0.43

1.2*

image08.png

0.27

0.21

0.6

* It is abnormal for the coefficient greater than 1. Refer to the Discussion on page 7.

C.

...read more.

Conclusion

Also, we can ensure the applied force is horizontal by fixing the spring balance on a horizontal platform. If we pull the spring balance directly, the force may not be always horizontal and the useful horizontal component of the force will be smaller than the balance’s reading.

When pulling the plank, the spring balance’s reading represents the frictional force. When pulling the blocks directly, the reading represents the applied force, which may not be equal (in magnitude) to the friction.

Q.17        In pushing a car (with the engine detached from the wheels), explain briefly why it is more difficult to start the motion, but once the car is moving, it is relatively easier to maintain its motion.

A.17        Limiting static friction is greater than kinetic friction. Especially for a car with mass generally over 1000 kg, the reaction force is very large. So the difference of magnitude between these two types of friction is very significant for a human.

Q.18        In the design of the braking system in bicycles, what parameter(s) should be maximized to achieve a larger frictional force?

A.18        The reaction force exerted on the braking pads and the coefficient of kinetic friction should be maximized.

8. Conclusion

This experiment was quite successful. It demonstrated that friction is directly proportional to normal reaction but independent of contacting area. Also, coefficients of static and kinetic friction can be compared.

~ End ~

P.

AL-PHY-TAS 4 (A1) - Full Report

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Mechanics & Radioactivity 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

See related essaysSee related essays

Related AS and A Level Mechanics & Radioactivity essays

  1. Investigating Force, Mass and Acceleration using a Trolley

    The track might be slightly incline due to the table or the floor which the track is not perpendicular to the gravitational force of earth and create an unwanted force in the system. For example The unwanted force ((MA + M)g Sin a)

  2. Centripetal motion. The objective of this experiment is to verify whether the tension ...

    It can increase the accuracy in time-recording. 3. Lubricants such as oil and Vaseline can be smeared at the upper mouth of the glass tube so that the friction between the string and the upper mouth of the glass mouth can be reduced.

  1. Perform an experiment on friction and the variables of friction using a wooden block, ...

    When the experiment was carried out, as I predicted, when the weight on the block increased so therefore did the Newton's required to move it from a fixed position. The test was done with 2 Newton meters over 2 days. Using the same Newton meter was impossible as it broke.

  2. Investigating the factors affecting tensile strength of human hair.

    Different people measured hair thickness and recorded it to what they felt the thickness ought to be according to the scale. It was not very clear to see how thick the hair was, as the hair was faded under the microscope at all magnifications and the outline was difficult to see.

  1. Use of technology in a hospital radiology department. The department of imaging is one ...

    activities and to check that the company are complying with health and safety law. Then the inspector may offer guidance or advice to help you maintaining your workplace properly. The inspector will decide what action to take; the action will depend on the nature of the breach and will be

  2. Centripetal Force

    Hence explain why a choice of is made in this experiment. From question 3, . Thus, a larger value of (i.e. 5) is chosen in order to make as small as possible. As decreases when � decreases, in that way, � can be kept small.

  1. The physics involved with a rollercoaster.

    In a "NEGATIVE 2 g" environment it would take 200 lbs to hold the rock down on the ground. In a "-5 g" environment it would take 500 lbs to hold the rock down to the ground. If the rock were put into a "zero g" environment then it would be weightless.

  2. Given a Batch of Factory Springs, Estimate the Average Spring Constant and Uncertainty of ...

    I will check the weights of the loads on electronic scales to ensure they are correct. I will add the weights in 1 N loads, starting with 2N, and record the extension (?x) in cm. I will do this until 10 N have been added.

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