ch.3

Question 1

What is the primary role of gravity in the universe?

Answer 1

Gravity gives the universe its structure and is the force that causes all objects to pull on other objects everywhere.

Question 2

What kind of motion does gravity cause objects to undergo?

Answer 2

Orbital motion and elliptical paths.

Question 3

Was Newton the first to claim gravity was responsible for celestial motion?

Answer 3

No, he was not the first, but he was the first to study the properties of gravity and write the equations of gravity-induced motion.

Question 4

According to Newton’s 1st law, how does the speed at which an object is thrown affect its landing distance?

Answer 4

If thrown at low speed, it lands closer; if thrown faster, it reaches a farther distance.

Question 5

What happens at a high speed that allows an object to enter orbit?

Answer 5

The object can travel so far that the ground curves from underneath it.

Question 6

What is Newton’s law of universal gravity equation?

Answer 6

𝐹𝑔 = 𝐺 𝑀×𝑚

Question 7

What does Newton’s second law state?

Answer 7

𝑎 = 𝑣² / 𝑟

Question 8

What is surface gravity?

Answer 8

The acceleration a mass undergoes at the surface of a celestial object.

Question 9

What factors can surface gravity influence?

Answer 9

• Weight of a mass at a celestial object’s surface
• Shape of a celestial object
• Presence of an atmosphere

Question 10

What is Kepler’s modified 3rd law formula?

Answer 10

M = (4π²r³)/(GP²)

Question 11

What is the surface gravity on Earth?

Answer 11

9.8 m/s²

Question 12

What is the surface gravity on the Moon?

Answer 12

1.6 m/s²

Question 13

What is the ratio of surface gravity between Earth and the Moon?

Answer 13

Gearth/Gmoon = 6

Question 14

What is the escape velocity?

Answer 14

The certain speed that a mass must obtain to overcome a celestial object’s gravitational pull.

Question 15

What does escape velocity determine?

Answer 15

• If a spacecraft can move from one planet to another
• Whether a celestial object has an atmosphere
• The characteristics of black holes

Question 16

How does the mass of an object affect its escape velocity?

Answer 16

The smaller the mass, the lower the escape velocity; the larger the mass, the higher the escape velocity.

Question 17

What is the escape velocity on the Moon?

Answer 17

2.4 km/s

Question 18

What is the escape velocity on Earth?

Answer 18

11 km/s

Question 19

What is the escape velocity formula?

Answer 19

Vesc = (2GM/R)^(1/2)