This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

Sunday, October 11, 2009

Simple Machines – The Inclined Plane

This article was originally published in Oct 2008.

As with all machines, if we want the force exerted by the effort to be less than the force exerted by the load, the distance travelled by the effort has to be more than the distance travelled by the load.

Below are 4 illustrations how the inclined plane works.



The more gradual the slope, the greater the distance travelled by the effort compared to the distance travelled by the load. This means that the more gradual the slope, the less effort is needed to move the load.

Examples of applications of the ramp in real life – wheelchair ramps for the disabled, gradual and winding slopes of a road found in mountainous terrain (e.g. roads to Gentling Highlands or Cameron Highlands).



It can be noted that the ‘sharper’ the wedge, the less the effort is needed because for the same distance travelled by the effort, the distance moved by the load is now less.

Examples of applications of the wedge in real life – axe head, blades of knives, metal wedges for prying open flanges of pipes in heavy industries.



Fig 1 - For every 1 turn the screw makes, the screw is driven down by the distance of ‘1 pitch’. Hence, the more gradual the slope of the thread, the smaller the distance it will be between 2 threads, as shown in Fig 2.

Fig 2 - the distance travelled by the load is less than in Fig 1, although in both cases, the effort moves by the same one turn. Since the load moves less in Fig 2, less effort is also needed.

In conclusion, for screws, the more the number of threads there is, OR the smaller the pitch, OR the more gradual the slope of the threads, the less the effort is needed to move the load.



Again, like the screw, the smaller the pitch, the less the ends of the ‘V’ move towards each other, which also means the less the distance the load moves.

Like the screw, for the screw jack, the more the number of threads there is, OR the smaller the pitch, OR the more gradual the slope of the threads, the less effort is needed to move the load.

Take note that for the screw jack, while the mechanism of the inclined plane is used to lift the vehicle off the ground, the handle of the screw jack works on the principle of the wheel and axle. In this case, the handle is the wheel, while the screw of the jack (the part with the threads) is the axle.


Important note to parents and students – The purpose of the above 4 illustrations is to help students understand the mechanics of the inclined plane. Most schools’ practice papers and science textbooks do not use the terms ‘pitch’ or ‘threads’. Those terms are technical terms used in the heavy and light industries.

In trying to make the illustration as simple as possible, I have found that I cannot avoid using those technical terms. The use of the above terms is to assist the student (or parent) to understand the mechanics of screws and screw jacks.

Take note that markers who will be marking your Science PSLE Paper, in all likelihood have been teachers all their lives and may not have worked in industries before, and would probably not be familiar with the terms ‘pitch’ and ‘threads’.

In other words, it is highly advised that you do not use the terms ‘pitch’ and ‘threads’, unless you are able to draw and label the diagrams as accurately as the above.

18 comments:

keentolearn said...

Dear Mr Song

For inclined plane, the distance travelled by the effort and load appears to be the same eg if you push a drum of oil up a inclined plane to a lorry, the effort(push) and load(drum) move the same distance up an inclined plane.I always find it confusing

Observer said...

When you want climb up the mountain, you basically want to move from the base to the peak. This is the distance the load should move. How the load actually moves in between is the actually the movement of effort and not the load. By the way, mountain road is an inclined plane.

So to move a load up a lorry, the distance you want the load to move is from the road up the lorry, the vertical distance. How you actually move it is the effort. Whether you use a steep inclined plane or a more gradual inclinded plane will decide the distance the effort travels.

Excel Eduservice said...

To keentolearn -

The effort is the movement up the slope.

The load is the VERTICAL movement against gravity.

The idea of the ramp or slope, is to work AGAINST the FORCE OF GRAVITY, which is the vertical downward pull.

keentolearn said...

Dear Mr Song

Thank You for your reply.

Tilted Earth said...

Dear Mr Song

Can plants that have no green leaves still make their own food?

Excel Eduservice said...

Yes.

Tilted Earth said...

Dear Mr Song

Why is the use of gears necessary in a manual egg beater?

Excel Eduservice said...
This comment has been removed by the author.
Excel Eduservice said...

Do you have a manual egg-beater? If you do, it is easier to explain to you. Manually make turn the handle one full round. Observe how many rounds the beater turns in response. Then observe the number of teeth that is attached to the handle, and compare that to the number of teeth that is attached to the beater.

You will notice that the number of teeth on the handle side is many times more than the beater.

The purpose of the gears is to increase the distance moved by the load by many more times than the distance moved by the effort.

tilted earth said...

Dear Mr Song

Thank You for your reply.

I've not seen a manual egg beater, but from its picture in the book, I observed that there is a change of direction when the handle is turned.

Am I correct?

Tilted Earth said...

Dear Mr Song

Can seeds germinate in a flask of pond water covered by a layer of oil?

Tilted Earth said...

Dear Mr Song

Q1)Is it possible for seeds to germinate if they are buried under the soil?

Q2)Can seeds germinate in a flask of pond water covered by a layer of oil?

Tilted Earth said...

Dear Mr Song

In the experiment set up, there are two air tight containers. A contains a piece of bread mixed with a few drops of water. B has a piece of bread. After three days, it was given that the bread at the container A was mouldy and the bread at container B was less mouldy.

Q1) The containers are airtight. How does this make the experiment a fair test?

Q2) A third piece of bread was heated in an oven. What do you expect to see when this bread was put in another airtight container after three days?

Tilted Earth said...

Dear Mr Song

In this question, there was a table showing the composition of three air samples. The volume of each sample is 100 cubic centimeter.

Part B of the question asked which activity used up more oxygen, sleeping or running. Explain your answer. (1 mark)

The following answer was given zero marks. ----- Running. When we are running, our lungs need to take in more oxygen so that the heart can pump more blood containing oxygen and digested food to the various parts of the body to produce the amount of energy needed.

Your advice, please.What is the most appropriate way to answer this question.

Tilted Earth said...

Dear Mr Song

When hot buns are taken from the oven and covered with a piece of plastic food cover, the food cover would turn misty after a few minutes. Is it correct to say that hot water vapour from the buns condensed on the cool cover to form water droplets? Or, it is more appropriate to say that water vapour from the surrounding air within the food cover received heat from the buns,it then condensed on the cooler cover to form water droplets?

ping an said...

Dear Mr Song

http://www.wendykoh.com/08/primary6-taonansa1-science.pdf

Please refer to Q35.Is the height of the metal stand important to ensure that it is a fair test?I think the distance between the two metal stands is more significant?

What's your advice?

Excel Eduservice said...

Ping An,

I agree with you that distance between the 2 metal stands is more important than the height.

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