THEME: INVESTIGATING FORCE AND ENERGY

Examples of activities that involve a pushing force.

Examples of activities that involve a pulling force.

Examples of activities that involve both pulling and pushing.

Effect of a force.i) An object will

change its shape when a force is exerted on it.

i) A force can change the direction of a moving object.

ii) A force can make an object move fast or slowly.

iii) A force can stop a moving object

•Rough surfaces such as sand paper and carpets produce greater frictional force.•Smooth surfaces such as glass and rubber mats produce smaller frictional force. •If two objects are pushed with the same force, the object that moves on a smooth surface moves faster due to the smaller frictional force.

•A heavier object produce greater frictional force.

This force oppos

es motio

n

SPEED Every object that moves has speed. Speed shows how fast an object moves. An object which moves faster travels a longer distance in a

given time. An object which moves faster takes a shorter time to travels in a

given distance. To speed of an object can be calculated by using the following

formula:Speed = Distance Time

Examples : a)A lorry takes three hours to reach a destination of 240 km away.

Speed = 240 = 80 km/hour 3

b)A toy car takes 2 minutes to travel a distance of 50 cm.Speed = 50

2= 25 cm/min

Increasing and decreasing friction:a) Using rollers or ball bearing

b) Using lubricants such as oil , wax or grease.

c) Using talcum powder or air cushion.

d) Smoothing the surfaces.

e) Using an aerodynamic shape.

a) Using rough materials.

b) Making patterns on the surface.

FOOD PRESERVATION

The concept of food preservationThe following are different types of food preservation:a) Drying This method removes water from food. It can be done by sunning food. This method can prevent the growth of microorganisms because

bacteria and moulds cannot grow without the presence of water.

Fishes are dried in the Sun.

b) Smoking Food is preserved and flavoured through the use of smoke. The heat and aroma from the smoke dry and preserve food without

cooking it.

Fishes are smoked until they become dry.

Inside the smoke place

C) Salting. Salt is used to preserve food such as fish, eggs and fruit. Salting can be done by soaking food in a concentrated salt solution. Salting can prevent the growth of microorganisms on food. This process changes the taste and colour of food.

d) Pickling. Pickling is the method of preserving food by placing it in a solution

such as vinegar, salt or sugar. Salt, sugar and vinegar solution retard the growth of bacteria and

fungi on food. Food that is preserved in this way has its taste and colour changed as

well as its nutrient content reduced. Examples of food that can be preserved in this way are papayas,

mangoes, guavas and chillies.

SALTSalted

fishSalted

egg

e) Cooling. The temperature for cooling food is between 0°C to 5 °C. Low temperatures prevent the growth of bacteria and fungi. Cooling does not kill bacteria but only prevents them from

growing. Bacteria and fungi will be active again after food is taken out from

the refrigerator so food must be cooked or eaten immediately. Food that can be preserved by cooling are vegetables and fruit.

f) Vacuum packing. This method of preserving food is done by keeping food in a

condition without air. The steps involved in this method are: Food is kept in a plastic bag. The air inside the plastic bag is pumped out. The vacuum plastic bag is then sealed or tightly closed. Bacteria and fungi cannot breed without the presence of air. Food that can be preserved in this way includes roasted peanut

fruits and biscuit.

g) Canning and bottling. This method involves the process of heating food to kill bacteria

and storing it in airtight containers. This method enables food to be kept for a very long period up to a

few years. Bacteria and fungi cannot breed without the presence of air. The steps involved in canning are:a) Food is cut and cleaned.b) The food is then heated or cooked.c) The food is kept in a can and heated again.d) The can is sealed when the food is still hot.

h) Boiling. In this process, food is heated to the boiling point of water, that is

100°C for 30 minutes. This temperature can kill microorganisms. Examples of food preserved by using this method are fruit, jelly and

jam.

SARDINES

i) Freezing. In this method, food is kept at very low temperatures, as low as -15°C. The very low temperature and lack of water prevent the growth of

microorganisms. However, frozen food must be cooked immediately after taking out

from the freezer because bacteria becomes active at room temperature.

j) Pasteurising In this process, food is heated to a specific temperature for a certain

period. The taste and nutrient content of food do not change and can be

maintained. This process is usually used for milk and fruit juice.

Milk

k) Waxing. Wax such as beeswax is coated onto surface of food such as fruit

and vegetables. Wax is used to replace the natural wax produced by food and it can

keep food dry. This method can increase the shelf life of food for more than two

weeks.

The Importance of preserving food. To make food last longer. To store food easily. To reduce wastage of food. To ensure that food is safe for consumption. To protect food against microorganisms.

The Effects Of Improper Waste Disposal On The

Environment.

Improper Ways Of Waste Disposal

Waste Effect

Effects of improper waste disposal

Bad smell

Air pollution:It is cause by open burning , forest fires, releasing smoke from factories and vehicles.

Affect health- People will have respiratory problem

Acid rain-Smoke and gases that come from factories and vehicles dissolve in rain water to form acid.- It cause iron to become rusty.

Water Pollution-Rubbish and waste are thrown into the river , drain and sea. The sources of water become polluted.-The toxic waste can kill the aquatic animals. It will reduce the content of oxigen in the water.

Breeding place for germs and pest

Flash flood-The improper waste disposal will clog up the river and the drain that will prevent the flow of water.-The water will overflow into the land.-It will cause flash floods during heavy rain.

The proper ways to dispose

rubbish by local

authority

Waste is also burnt in an incinerator

Garbage truck will collect waste The waste is sent

to landfill

How to improve waste disposal

Use biodegradable plastic

Process the waste as food for farm

animals

Reuse the recycle material

Waste Decay

Eclipses…….

Eclipse of the Moon………..

The Phenomenon of an eclipse

An eclipse of the moon occurs when the Earth is between the Sun and the Moon.

During this eclipse , the Moon will appear dark because the Earth blocks sunlight from reaching the Moon.

An eclipse of the moon can only be observed at night.

An eclipse of the moon occurs during

the phase of full moon.

An eclipse of the Moon occurs in stages as shown below:

V

X

W

Z

Y

V : No eclipse

W : Partial eclipse

X : Total eclipse

Y : Partial eclipse

Z : No eclipse

Eclipse of the Sun……………

The eclipse of the Sun occurs when the Moon is between the

Sun and The Earth in a straight line.

The Moon blocks sunlight from

reaching the Earth.

The shadow of the Moon will cover a part of the Earth’s surface.

Moon

Earth

Sun

wxy

Sun

Moon W : Partial eclipse

Y : Partial eclipse

x : Total eclipse

Simple Machines………..

The ancient Egyptians were very clever.They figured out how to use the lever.They built pyramids with stones that weighed a lot.Inclined planes helped to move them to the right spot.Why not use wheels?I’m not certain.History sometimes holds mysteries behind a time curtain.Did the Egyptian invention work out?See a pyramid and you have no doubt

Simple Machines

A device that allows us to use less force to do work.

Help us to do work easily, quickly and conveniently.

Types of simple machines:LeverGearScrewWheel and axleInclined plan wedge

Type Example

1.   Pulley -

A pulley is a simple machine that uses grooved

wheels and a rope to raise, lower or move a load.

2.   Lever -   A lever is a stiff bar that rests on a support called

a fulcrum which lifts or moves loads. 

 

3.   Wedge - A wedge is an object with at least one slanting

side ending in a sharp edge, which cuts material

apart.

4.   Wheel & Axle -

A wheel with a rod, called an axle,

through its center lifts or moves loads.

5.   Inclined Plane - An inclined plane is a slanting

surface connecting a lower level to a

higher level.

6.   Screw - 

A screw is an inclined plane wrapped

around a pole which holds things

together or lifts materials.

7. Gear -

Gear is a wheel with jagged edges

like teeth. Use to change the speed

of object and change direction of

movement.

Complex Machines

Meaning

A tool that has more than one simple machine.

Examples of Complex Machines

Scissors

• Wedge, lever, Screw

Wheelbarrow

• Lever, wheel and axle.

Hand drill

• Wedge, Screw, gear, wheel and axle