SPI 0807.12.5 Gravity

Bell Work (IF) Reword and answer Put lab sheet (HW) in the basket. Pick up a glue stick, full sheet, and a half sheet. Answer the following: What is the relationship between mass and gravity? What is the difference between mass and weight? Start a new section called “Gravitational Attraction.”

Objective: Determine the relationship among the mass of objects, the distance between those objects, and the amount of gravitational attraction.

Brainpop: Gravity

The Law of Universal Gravitation Gravity is an attractive force that pulls objects toward each other. Gravity is the force that keeps you grounded on Earth and prevents you from floating off into space.

Law of Universal Gravitation Just as you are attracted to Earth, Earth is attracted to you as well. You also attract all the other objects around you. However, your gravity is much, much smaller than Earth’s, so you do not notice it.

2 variables that affect gravitational force: 1. Mass 2. Distance. The more mass an object has, the more gravitational attraction it exerts on other objects. As the distance between objects increases, the force of gravity between them decreases.

Gravitational Force: Mass The gravitational force between two objects depends on two factors: mass and distance. What is mass?

Gravitational Force: Mass Which has the strongest gravitational attraction and why?

Gravitational Force For small objects, such as two apples, this force is barely measurable. Why?

Gravitational Force However, for larger objects, such as Earth and a weather satellite, the force is much greater. Earth’s mass is so great it exerts a strong gravitational force on a satellite. This is why a satellite does not fly off into space as it is moving rapidly around Earth.

Gravitational Force: Distance Distance also affects the force of gravity between two objects. As the distance between objects increases, the force of gravity between them decreases. Likewise, as the distance decreases, the force of gravity increases. WHAT!!!???!!???? Let’s look at an example.

Gravitational Force: Distance If each ball has the same mass, which has the strongest gravitational attraction and why?

Guided Practice Which of the following pairs of objects would have the greatest attraction toward each other due to gravity? Least? A. a 8 kg object and a 8 kg object, 2 m apart B. a 3 kg object and a 3 kg object, 2 m apart C. a 8 kg object and a 8 kg object, 4 m apart D. a 3 kg object and a 3 kg object, 4 m apart

Guided Practice Which of the following pairs of objects would have the greatest attraction toward each other due to gravity? Least? A. a 8 kg object and a 8 kg object, 2 m apart B. a 3 kg object and a 3 kg object, 2 m apart C. a 8 kg object and a 8 kg object, 4 m apart D. a 3 kg object and a 3 kg object, 4 m apart

Independent Practice Which of the following pairs of objects would have the greatest attraction toward each other due to gravity? A. a 12 kg object and a 12 kg object, 6 m apart B. a 7 kg object and a 7 kg object, 6 m apart C. a 12 kg object and a 12 kg object, 4 m apart D. a 7 kg object and a 7 kg object, 4 m apart

Independent Practice Which of the following pairs of objects would have the weakest attraction toward each other due to gravity? A. a 10 kg object and a 10 kg object, 4 m apart B. a 5 kg object and a 5 kg object, 4 m apart C. a 10 kg object and a 10 kg object, 2 m apart D. a 5 kg object and a 5 kg object, 2 m apart

Gravitational Force In other words, as objects move closer together, their pull on each other grows. As objects move farther apart, their pull on each other weakens. A good example is to consider a traveling spacecraft.

Gravity As the spacecraft moves away from Earth, the pull of Earth’s gravity becomes weaker. At the same time, as the spacecraft moves closer to another planet, the pull of that planet’s gravity increases.

Gravity and Orbits Since gravity pulls objects toward each other, what keeps the moon from crashing into Earth?

Inertia The answer is inertia, an object’s tendency to resist a change in it’s motion. We will discuss that next time. Please get out a sheet of paper and title it “Gravitational Attraction Assessment.”

1. What happens to the force of gravity between two objects if the distance between them increases? A. The pull of gravity increases. B. The pull of gravity decreases. C. The pull of gravity stays the same. D. The pull of gravity disappears.

2. In addition to distance, what factor determines the force of gravity between two objects? A. the volume of each B. the mass of each C. the diameter of each D. the chemical formula of each

3. Suppose you roll a basketball and a baseball toward each other. How does this affect the force of gravity they exert on one another? A. the pull of gravity increases B. the pull of gravity decreases C. The pull of gravity stays the same D. the pull of gravity disappears

4. How would the force of gravity be affected if Earth and the sun were closer together? A. The force of gravity would increase. B. The force of gravity would decrease. C. The force of gravity would stay the same. D. The force of gravity would disappear.

5. Which of the following pairs of objects would have the greatest attraction toward each other due to gravity? A. a 10 kg object and a 10 kg object, 4 m apart B. a 5 kg object and a 5 kg object, 4 m apart C. a 10 kg object and a 10 kg object, 2 m apart D. a 5 kg object and a 5 kg object, 2 m apart

6. If Earth and Jupiter were the same distance away from the sun, which planet would have a greater gravitational attraction to the sun and why? F. Jupiter would have a greater gravitational attraction to the sun, because Jupiter is more massive than Earth. G. Jupiter would have a greater gravitational attraction to the sun, because Jupiter has a larger volume than Earth. H. Earth would have a greater gravitational attraction to the sun, because Earth has a greater density than Jupiter. J. Earth would have a greater gravitational attraction to the sun, because Earth has a higher average temperature than Jupiter.

7. Scientists observe a distant star and the four planets that orbit the star. They determine that the four planets have different diameters, but approximately the same mass. This star system is represented by the diagram below. Which planet has the greatest gravitational attraction to the star?  A. Planet 1 B. Planet 2 C. Planet 3 D. Planet 4

8. How does the mass of two objects affect the gravitational attraction they exert on each other?

9. How does the distance between two objects affect the gravitational attraction they exert on each other? Explain.

10. What 2 factors keep all of the planets in the solar system in orbit around the sun?