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Natural sciences

Grade 9

Energy, forces and machines

Module 19

Forces and friction

Activity:

Describing and applying the terms force and friction

[lo 1.2; lo 1.3; lo 2.3; lo 2.4]

The sketch that follows represents a brick lying on a table in front of you. Discuss ways in which the brick could be made to move and decide on one method. In science we indicate forces and the direction in which they operate by means of an arrow.

Indicate the possible directions of motion by means of arrows.

  • How would you define a force?
  • You could have applied tractive power (pull) or thrust power. When you stop pulling or pushing the brick, it stops moving or comes to rest. Why? Another simultaneous force that opposed the force that you were applying must have been in operation. This force is known as FRICTION .

List examples of friction from common daily experiences.

Assessment

Were you able to describe the term “force”, indicate the lines of action on the sketch and provide examples of friction?

[LO 2.4]

Investigation: FORCES AND FRICTION

Use a stopwatch, a spring balance, a brick, a smooth piece of cardboard or perspex as big as the base of the brick, a length of string, some baby-powder and a skateboard.

  • Tie the brick to the spring balance, using the length of string.
  • Move the spring balance along slowly to bring the brick into motion, checking the balance to note the position of the needle when the brick begins to move.
  • Pull the brick over a distance of 5 metres – get someone to time this action and enter the information on a table.
  • Repeat this procedure, but secure the brick to the cardboard or perspex. Time the action and tabulate the details. Try to apply sufficient force for the needle to give the same reading as previously. Use same distance stretch for every procedure.
  • Repeat the procedure, but secure the brick to the skateboard.
  • Do three repeats of all of the above. Use baby powder as an alternative in all three and sprinkle on wheels of skateboard.

1. Why was it necessary to repeat the experiment three times?

2. Why did you get different time readings for the action when you pulled the brick only, the brick on cardboard or perspex and the brick on the skateboard?

3. Mention other methods by which friction can be reduced.

4. Think about a motor vehicle and list five examples to show that it is necessary to use a lubricant or some other method designed to reduce friction. Explain each example.

[LO 1.2; LO 1.3; LO 2.3]

Remember the following:

  • Forces can:
  • change the shape of an object;
  • increase or slow down the speed of an object;
  • redirect the motion of an object and
  • rotate an object around a fixed point.
  • There are forces of attraction or pull (tractive forces) and of thrust (push) and can both operate directly or over a distance.
  • Most forces, however, only come into operation when objects are in contact with one another.

Questions:

1. Provide an example of each of the following effects:

  • change of form
  • change of speed
  • forces that operate when there is no contact
  • forces of thrust

Activity:

Researching a scientist who made an important contribution to science: Isaac Newton

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
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Akash Reply
it is a goid question and i want to know the answer as well
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Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
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are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
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Cied
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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many many of nanotubes
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Source:  OpenStax, Natural sciences grade 9. OpenStax CNX. Sep 15, 2009 Download for free at http://cnx.org/content/col11069/1.1
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