Planetary Motion

Planetary Motion

The Moon, the planets, the Sun, and the stars all rotate around the Earth (which stays still), with uniform circular motion.

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​Geocentric Model

The Moon, the planets, the Earth, and the stars all rotate around the Sun (which stays still), with uniform circular motion.

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​Heliocentric Model

Multiple Choice

Heliocentric model is Earth-centered.

• True

• False

Multiple Choice

Geocentric model Earth-centered.

• True

• False

Fill in the Blanks

The earth is at the center according to

model.

Fill in the Blanks

The Sun is at the center according to

model.

Kepler's Laws of Planetary Motion

The planets move around the Sun in elliptical orbits.

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​Kepler's First Law

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A line running from the sun to the planet sweeps out equal areas of the ellipse in equal times.​

​Kepler's Second Law

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The squares of the orbital periods of the planets are directly proportional to the cubes of the semi-major axes of their orbits.

​Kepler's Third Law

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Multiple Choice

According to Kepler's Model planets travel in ____ orbits.

• elliptical

• circular

Multiple Choice

The closer a planet is to the sun the ____ distance is covered in the same time.

• more

• less

• same

Multiple Choice

The closer an orbiting object is to the sun, the _____ it travels.

• faster

• slower

Multiple Choice

Which force is required to maintain a body in uniform circular motion?

• Muscular force

• Gravity force

• Centripetal force

• Friction force

Multiple Choice

Which of the following is the correct definition of centripetal force?

• The force that acts away from the centre of the circle when an object is moving on a circular path, is known as centripetal force.

• The force that acts between two masses separated from each other by a certain distance, is termed as the centripetal force.

• The force that acts between two static charges separated from each other by a distance is termed as the centripetal force.

• The force that acts towards the center of the circle when an object is moving on a circular path, is known as centripetal force.

Multiple Choice

Which of the following changes when a body performs uniform circular motion?

• Mass

• Speed

• Kinetic energy

• Direction

Multiple Choice

When a girl rotates a stone tied to a string by swirling the string what force does her hand exert on the string?

• Centrifugal

• Centripetal

Multiple Select

What are the changes in a uniform circular motion?

• velocity changes

• direction changes

• speed changes

• mass changes

• acceleration changes

Multiple Choice

What is centrifugal force?

• The force that acts away from the centre of the circle when an object is moving on a circular path, is known as centrifugal force.

• The force that acts between two masses separated from each other by a certain distance, is termed as the centrifugal force.

• The force that acts between two static charges separated from each other by a distance is termed as the centrifugal force.

• The force that acts towards the center of the circle when an object is moving on a circular path, is known as centrifugal force.

Multiple Choice

What is the difference between centripetal and centrifugal forces?

• Centripetal is towards center while centrifugal is away from the center.

• Centrifugal is towards center while centripetal is away from the center.

Multiple Choice

Which of the following terms means "center fleeing"?

• centrifugal

• centripetal

Multiple Choice

Which of the following is the unit for centripetal force?

• J
• m/s²
• kg⋅m/s
• N

Multiple Choice

What is the relationship between centripetal force and the mass of an object?

• direct

• inverse

Multiple Choice

If centripetal force stopped acting on all satellites they would continue traveling in space in a constant direction and constant speed.

• True
• False

Multiple Choice

A car is rounding a bend as shown in the diagram. Which arrow correctly shows the direction of the cars velocity?

• A

• B

• C

• D

Multiple Choice

If car A and car B are both traveling at the same speed, which will require a higher centripetal force?

• Car A

• Car B

• They have the same centripetal force

Thank You