# Lesson Notes By Weeks and Term - Primary 6

OUR EARTH AND SKY

WEEK 5

SUBJECT: BASIC SCIENCE AND TECHNOLOGY

TERM: 1ST TERM

CLASS: PRIMARY 6

TOPIC: OUR EARTH AND SKY

BEHAVIOURAL OBJECTIVES: AT THE END OF THE LESSON, PUPILS SHOULD BE ABLE TO:

1. State the shape of the earth
2. State the meaning of gravitational force
3. explain the moon, sky and planet.

INSTRUCTIONAL MATERIALS:

A chart showing the instruments for measuring weather condition

REFERENCE MATERIALS

Scheme of work

All relevant materials

9-Years Basic Education Curriculum

Online information

BUILDING BACKGROUND/CONNECTION TO PRIOR KNOWLEDGE:

Pupils are familiar with the topic in their previous classes.

CONTENT OF THE LESSON

# Shape of the Earth

What is the shape of the earth? You might have the idea that the earth is flat. The earth is not flat, as you would think; it is round (spherical) in shape.

It is one of the nine planets that revolve round the sun. It consists of three parts:

• Land - mountains, rocks, hills, grassland, dry land, forest, desert. This is the part of the earth where human beings live.
• Water - oceans, seas, rivers, lakes, streams. This covers about two-thirds of the earth.
• Atmosphere - air, cloud. This is the mixture of gases that envelops the earth i.e., the mixture of gases that surround the earth's surface.

How do we know the earth is spherical?

We have good reasons to believe that the earth is round and not flat. The following are some of the reasons:

• When a ship appears the horizon, the top of the mast is seen before any other part owing to the curvature of the earth.
• We know that the sun rises at different times in different places.

If the earth were flat, the sun would rise at the same time in all places.

• When we take pictures from high altitudes through a telescope, the pictures show clearly that the earth is curved or spherical. It is not flat. (iv) Nobody has seen the edge of the earth; if it was flat people would have seen the edge.

The Earth’s Gravitational Pull

When something falls to the ground we say that it is pulled by a force. This force is known as the force of gravity. This means that the earth exerts a force on bodies that tends to pull these bodies towards the ground. This force is called gravitational force. Therefore any object thrown up would eventually come back to the ground because the force of gravity pulls it towards the ground.

Weight of objects on Earth

The effect of the pull of the earth on an object is measured by its weight. The greater the amount of matter an object contains, the greater its weight. Another name for the amount of matter is mass. The mass of an object is constant but the pull of the earth (known as gravity) varies from place to place. Thus the weight of an object depends on the gravity:

Weight (W) = mass (m) x gravity (g)

For example, a school bag full of books will weigh more than an empty bag of the same size if measured at the same place.

# Weight of Objects on the Moon

Scientists have found out that the earth is nearly four times as big as the moon, and that the weight of the earth is six times the weight of the moon. The moon, like the earth, exerts a pull on objects around it. The force of gravity of the moon is one sixth of the force of gravity of the earth. So an object that weighs 120 N on the earth will weigh only 20N on the moon. This means that an object weighs much less on the moon than it weighs on the earth. Despite this fact, the object still has the same mass.

# Sky

The sky is the space we look up to from the earth. It is the space high above the earth. It is farther than we can see. The sky immediately above us is blue owing to the earth's atmosphere.

Beyond this blue sky is the boundless black sky that we simply refer to as space.

Objects that can be seen in the sky (space) are: the sun, the stars, the moon and the other planets. The sun gives light both to the earth and moon. The moon revolves around the earth; therefore it is called the earth's satellite. This means that a satellite is described as an object that revolves round (orbits) a larger object. Jupiter, a planet, has as many as twelve satellites revolving around it.

Space Travel

Space Travel is the journeying of a space traveler, otherwise known as an astronaut, to explore the environment (space) outside the earth. Scientists who study space and the objects we can find in it are called astronomers.

One place that an astronaut can travel to is the moon. We have learnt that objects weigh much less on the moon than they weigh on the earth. This is why an astronaut wears a heavy space jacket so that he can walk on the moon. Even with the space jacket, an astronaut often hops about as if he cannot walk normally as he does on the surface of the earth

If an astronaut can jump one metre on earth, he will be able to jump six metres on the moon, because the pull of the moon's gravity on him is very slight.

The Sun as a Major Source of Energy

The sun is a huge ball of burning gas. It is about 150 million kilometers from the earth.

The brightness of the day, which gradually comes in as the sun rises from the east, shows that the sun is a source of light. Light and heat travel through space. The rays reach us by radiation and they heat up the earth.

Assessment & Evaluation:

1. State the shape of the earth
2. State the meaning of gravitational force
3. Explain the moon, sky and planet.

(WRAP-UP CONCLUSION)

Teacher goes over the topic once again to enhance better understanding.