Gravity: Page 86

Question: What two factors determine how much gravity an object has?

OBJECTIVE: Students will be able to explain why some objects have more gravity than others.

VOCABULARY: gravity mass weight

Write these questions onto page 86

SKIP ONE LINE BETWEEN EACH QUESTION

1. What is gravity?2. What objects have gravity?3. What two factors determine how much gravity an object

has?4. How can an object’s weight change?5. Why does the sun have so much gravity?6. How does the moon’s gravity affect the Earth?

What is Gravity?

Gravity is a force.

When you lift weights, kick a soccer ball or even jump in the air you are using force. All these examples require that the two objects involved touch one another

Your arms touch the weights, your foot touches the soccer ball and your feet touch the skateboard.

Gravity

Gravity is different than most forces, because the two objects involved don’t have to touch.

In 1666, Sir Isaac Newton saw an apple fall from a tree. He hypothesized that the same force that made the apple fall from the tree kept the moon from flying off into space.

Newton did not discover gravity, but he was the first person to explain how it works.

What Objects Have Gravity?

All objects have gravity, but not all objects have the same amount of gravity.

What Determines the Amount of Gravity?

Two things determine how much gravity an object has.

2. The distance the objects are apart.

1. The mass of the objects.

What’s the Difference between Mass and Weight?

Mass is the amount of matter in an object.

Mass is measured with a balance.

Mass does not change from place to place.

Weight is the gravitational pull on an object.

Weight is measured with a scale.

Weight changes as gravity changes.

Understanding GravityDraw and label the pictures below onto page 86.

Drawing 1 shows two objects attracting one another.

Drawing 2 shows two objects with more mass attracting one another. The greater the mass, the greater the gravity.

Drawing 3 shows two objects with a greater distance between them. The greater the distance the smaller the gravity.

More gravity than picture 1.

Less gravity than picture 1

The Earth’s Gravity

If all objects have gravity, then when you play basketball why isn’t the ball attracted to you?

Although you’re a very close distance from the basketball, you don’t have much mass.

The Earth has so much mass, that everything falls toward it.

The Sun’s Gravity

The Sun has so much mass that even the planets are pulled around by the Sun’s gravity.

The Sun contains 99.9% of the entire mass of our solar system.

How Does the Moon’s Gravity Affect the Earth?

The moon is the closest, biggest object to the Earth.

The moon’s gravity has one big effect on the Earth.

The position of the moon as it circles the Earth causes the water in the oceans to rise and fall. This rising and falling is called, tides.

1. What is gravity?2. What objects have gravity?3. What two factors determine how much gravity an object

has?4. How can an object’s weight change?5. Why does the sun have so much gravity?6. How does the moon’s gravity affect the Earth?

Gravity: Review page 86

Write the answers to these questions into your notes.

VOCABULARY

Gravity-an attractive force between two objects.

Mass- the amount of matter in an object.

Weight- the gravitational force on an object.