Grade Six Science

Did you have a good week? Are you doing lots of revision? Your special exam is right around the corner, so be focused on your work. Work hard and do well.

Last week we looked at pulleys. Do you remember what we found out? Do check yourself. i What is a pulley? ii Describe a pulley. iii Name at least two places where pulleys can be found. iv Draw a fixed pulley. Draw a moveable pulley.

This week we will investigate another simple machine, the wheel and axle.

The wheel is a great invention. We can hardly do without it. The wheel by itself, however, is not a simple machine. A wheel by itself is simply a roller. Maybe the idea of a wheel came about from rolling logs along the ground many years ago. The wheel and axle has been around for some 7,000 years.

The wheel is part of a simple machine called the wheel and axle. The axle is a smaller wheel fitted tightly in the larger wheel. It works along with the larger wheel.

A windlass

Every time you turn a doorknob you are using a wheel and axle. If there were no knobs on the rod that goes through a door, it would be difficult to open the door. The knob makes it easier to work the latch.

The knob is a wheel. The rod is an axle. The wheel and axle work together to open the door. A wheel and axle is used in many machines. The wheel and axle helps to do work in many ways. This simple machine makes it easy to turn things and to move things. The wheel is attached to the axle so that these two parts rotate together. Here a force is transferred from one to the other.

Do you know what a windlass is? If you don’t, please find out before moving on. A windlass is a kind of wheel and axle. It has a horizontal axle for hauling or hoisting.

The principle of the windlass

Would you like to make your own windlass? Your windlass will help you to see how a wheel and axle moves things.

You will need nails, rope/string, screw eyes (curtain rods screw eyes), a small wheel (about 15cm in diameter), a large wheel (about 30cm in diameter), a base made of wood (about 30cm wide by 60cm long), a wood rod (about 60cm- a broom or mop stick will do) and two side blocks. Look carefully at the picture.

Now turn one wheel completely around. Observe the distance through which your load is moved. Turn the other wheel completely around and also observe the distance through which it is moved. You will find that whether the small wheel or the big wheel is used the distance is the same. Experiment with your wheel and axle as much as you would like to.

Experimenting with your wheel and axle

Large wheels are used on a wheel and axle to make work easy. Scientists have found that the larger the wheel, the easier the work. Large trucks, for example, have big steering wheels. The large steering wheel makes it easy for the driver to guide the truck. It would be quite difficult to get a truck around a corner with a small steering wheel.

Try to identify places where the wheel and axle can be found and identify them. Did you check your egg whisk and all those knobs that you turn? Do you see how simple machines help to make work easier and improve the quality of our lives?

Here are a few questions for you. 1. Name five classes of simple machines. 2. Place X near to each correct example of a simple machine. (a) pulley._______________ (b) wheel.________________ (c) scissors________________ (d) wheel and axle___________ (e) steps___________________ (f) seesaw__________________ (g) drink opener_______________ 3. _____________,_________________,_____________ are all examples of lever. 4. State three functions of simple machines. 5. Which simple machine does one usually find on a flag pole? 6. Name at least six wheel and axles.

Next week, D.V. we will look at Inclined Planes and Wedges. Until then, goodbye.

Hence, Total frequency = (10 + 4 + 2 + 4 = 20) Let us convert the above data into percentages: Amount spent on rides: 10/20 × 100 = 50% Amount spent on toffees: 4/20 x 100 = 20% Amount spent on popcorn: 2/20 x 100 = 10% Amount spent on ice-cream: 4/20 × 100 = 20%

That’s it, boys and girls! Can you work an exercise on your own? Yes, I know you can!

Complete the exercise below.

Exercise 1

The Pie Chart below shows the mode of transportation used by students of Grade 6 of Flower Primary School. a) Calculate the total number of students in the class. b) Convert into percentage, the number of students who go to school by:

i. Bus iii. Bike

c) Calculate the total percentage of students who go to school by bus and train.

d) How many more students use bus compared to train?

Great Job, boys and girls!

ii. Car iv. Train