Gravity Chapter 4 Lesson 21 TCAP Coach. Objectives SPI 0507.12.1 Recognize that the Earth attracts objects without touching them. SPI 0507.12.1 Recognize.

GravityGravity

Chapter 4Chapter 4

Lesson 21Lesson 21

TCAP CoachTCAP Coach

ObjectivesObjectives

SPI 0507.12.1 Recognize that the SPI 0507.12.1 Recognize that the Earth attracts objects without Earth attracts objects without touching them.touching them.

SPI 0507.12.2 Identify the force that SPI 0507.12.2 Identify the force that causes objects to fall to the Earth.causes objects to fall to the Earth.

SPI 0507.12.3 Use data to determine SPI 0507.12.3 Use data to determine how shape affects the rate at which a how shape affects the rate at which a material falls to Earth.material falls to Earth.

GravityGravity

You know what happens when you jump You know what happens when you jump up into the air.up into the air.

You push off the ground, rise, and then You push off the ground, rise, and then move back toward the ground.move back toward the ground.

When you throw a ball up into the air, you When you throw a ball up into the air, you know what will come back down.know what will come back down.

These things happen because of a force These things happen because of a force called gravity.called gravity.

In this lesson, you will investigate gravity In this lesson, you will investigate gravity and learn about the factors that affect it. and learn about the factors that affect it.

The Force of GravityThe Force of Gravity

GravityGravity is an attractive force that pulls is an attractive force that pulls objects toward each other.objects toward each other.

Gravity Gravity attractsattracts objects even if the objects even if the objects do not touch.objects do not touch.

You probably think of gravity as a force You probably think of gravity as a force pulling objects toward the ground.pulling objects toward the ground.

In our everyday life, gravity really In our everyday life, gravity really pullspulls objects toward Earth’s objects toward Earth’s center.center.

But this force acts everywhere in the But this force acts everywhere in the universe- not just on Earth.universe- not just on Earth.

The Force of GravityThe Force of Gravity

Any object with mass exerts a force of Any object with mass exerts a force of gravitygravity that pulls on objects around it. that pulls on objects around it.

The more The more massmass an object has, the greater an object has, the greater its pull of gravity.its pull of gravity.

Gravity keeps you from Gravity keeps you from floating floating off into off into space.space.

Gravity helps keep the moon in Gravity helps keep the moon in orbit orbit around Earth.around Earth.

Gravity also helps keep Earth in Gravity also helps keep Earth in orbitorbit around the sun.around the sun.

The Force of GravityThe Force of Gravity

Just as you are attracted to Earth, Just as you are attracted to Earth, Earth is also attracted to you.Earth is also attracted to you.

You only notice the force that Earth You only notice the force that Earth exerts on you because your exerts on you because your attractive force is so much attractive force is so much smallersmaller..

The force of gravity depends on The force of gravity depends on twotwo factors. These two factors are factors. These two factors are massmass and and distancedistance..

How Mass Affects GravityHow Mass Affects Gravity Recall that Recall that massmass is the amount of matter is the amount of matter

in an object.in an object. An object with more mass has a An object with more mass has a greatergreater

force of gravity than an object with force of gravity than an object with lessless mass. mass.

Think about an apple and Earth.Think about an apple and Earth. Both objects pull on each other because Both objects pull on each other because

they both have mass. But because the they both have mass. But because the apple’s mass is so small, its force of apple’s mass is so small, its force of gravity is very gravity is very smallsmall..

It does not pull very strongly on Earth.It does not pull very strongly on Earth.

How Mass Affects GravityHow Mass Affects Gravity

Earth has much more Earth has much more massmass than an apple. than an apple. That means Earth has a larger That means Earth has a larger forceforce of of

gravitygravity than the apple. than the apple. This causes you to see the apple moving This causes you to see the apple moving

toward Earth rather than Earth moving toward Earth rather than Earth moving toward each other.toward each other.

Earth only moves the tiniest amount Earth only moves the tiniest amount because Earth’s because Earth’s pullpull is so much greater is so much greater than that of the apple.than that of the apple.

How Distance Affects GravityHow Distance Affects Gravity

The second factor that determines The second factor that determines the force of gravity between two the force of gravity between two objects is their objects is their distancedistance from each from each other.other.

As objects move closer together, As objects move closer together, their pull on each other their pull on each other growsgrows..

As objects move farther apart, their As objects move farther apart, their pull on each other pull on each other weakensweakens..

How Distance Affects GravityHow Distance Affects Gravity

Think of a spacecraft traveling Think of a spacecraft traveling toward another planet.toward another planet.

As the spacecraft moves away from As the spacecraft moves away from Earth, Earth’s pull on it Earth, Earth’s pull on it decreasesdecreases..

As the spacecraft moves closer to As the spacecraft moves closer to another planet, the other planet’s another planet, the other planet’s pull pull increasesincreases. .

How Distance Affects GravityHow Distance Affects Gravity

Friction and Air ResistanceFriction and Air Resistance

When objects fall to Earth’s surface, When objects fall to Earth’s surface, gravity is not the only force that acts gravity is not the only force that acts on them.on them.

FrictionFriction also affects their motion. also affects their motion. FrictionFriction is a force that acts between is a force that acts between

the surfaces that touch each other.the surfaces that touch each other. Friction tends to slow an object’s Friction tends to slow an object’s

motionmotion..

Friction and Air ResistanceFriction and Air Resistance

When an object falls through the air, When an object falls through the air, its surface bumps into air particles.its surface bumps into air particles.

Friction between a moving object and Friction between a moving object and air particles is called air resistance.air particles is called air resistance.

Air resistanceAir resistance acts against the pull acts against the pull of gravity to slow a moving object.of gravity to slow a moving object.

Friction and Air ResistanceFriction and Air Resistance

Air resistance depends on an object’s Air resistance depends on an object’s shapeshape and and surface areasurface area. .

A folded parachute falls to the ground A folded parachute falls to the ground much faster than an open parachute.much faster than an open parachute.

An open parachute’s cupped shape causes An open parachute’s cupped shape causes it to hold and touch more air particles as it it to hold and touch more air particles as it falls.falls.

Its large surface area also gives it more Its large surface area also gives it more air resistanceair resistance..

That slows a sky diver’s fall to the ground.That slows a sky diver’s fall to the ground.

Friction and Air ResistanceFriction and Air Resistance

1. The force of gravity will be 1. The force of gravity will be greatest between Earth and greatest between Earth and

A. an object with a mass of 4 kg.A. an object with a mass of 4 kg. B. an object with a mass of 30 kg.B. an object with a mass of 30 kg. C. an object with a mass of 200 kg.C. an object with a mass of 200 kg. D. an object with a mass of 1000 kg.D. an object with a mass of 1000 kg.

1. The force of gravity will be 1. The force of gravity will be greatest between Earth andgreatest between Earth and

D. an object with a mass of 1000 kg.D. an object with a mass of 1000 kg.

2. How does the distance between 2. How does the distance between objects affect the force of gravity objects affect the force of gravity

between them?between them?

A. The greater the distance, the A. The greater the distance, the greater the force of gravity. greater the force of gravity.

B. The smaller the distance, the B. The smaller the distance, the greater the force of gravity.greater the force of gravity.

C. The smaller the distance, the C. The smaller the distance, the smaller the force of gravity.smaller the force of gravity.

D. Distance has no effect on the D. Distance has no effect on the force of gravity.force of gravity.

2. How does the distance between 2. How does the distance between objects affect the force of gravity objects affect the force of gravity

between them?between them?

B. The smaller the distance, the B. The smaller the distance, the greater the force of gravity.greater the force of gravity.

3. Which BEST describes the 3. Which BEST describes the gravitational attraction between an gravitational attraction between an

apple and Earth?apple and Earth?

A. Earth attracts the apple.A. Earth attracts the apple. B. The apple attracts Earth.B. The apple attracts Earth. C. The apple and Earth attract each C. The apple and Earth attract each

other.other. D. The apple has no gravity.D. The apple has no gravity.

3. Which BEST describes the 3. Which BEST describes the gravitational attraction between an gravitational attraction between an

apple and Earth?apple and Earth?

C. The apple and Earth attract each C. The apple and Earth attract each other.other.

4. Which two objects have the 4. Which two objects have the MOST gravitational attraction MOST gravitational attraction

toward each other?toward each other?

A. two basketballs one foot apartA. two basketballs one foot apart B. two golf balls one foot apartB. two golf balls one foot apart C. one basketball and one golf ball C. one basketball and one golf ball

one foot apartone foot apart D. two basketballs two feet apartD. two basketballs two feet apart

4. Which two objects have the 4. Which two objects have the MOST gravitational attraction MOST gravitational attraction

toward each other?toward each other?

A. two basketballs one foot apartA. two basketballs one foot apart