Unit 9: Orbits and Gravity Study Guide

Newton’s first law of motion states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by what?

• A net external force

• Gravity

• Friction

• Inertia

Newton's second law of motion states that

• the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass

• an object at rest stays at rest and an object in motion stays in motion unless acted upon by a net external force

• for every action, there is an equal and opposite reaction

• energy cannot be created or destroyed, only transformed from one form to another

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Newton’s third law of motion states that:

• For every action, there is an equal and opposite reaction.

• An object in motion stays in motion unless acted upon by an external force.

• Force equals mass times acceleration.

• Energy cannot be created or destroyed.

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The difference between mass and weight is:

• Mass is the amount of matter in an object, while weight is the force exerted by gravity on that object.

• Mass is measured in newtons, while weight is measured in kilograms.

• Mass changes with location, while weight remains constant.

• Mass and weight are the same and can be used interchangeably.

On the diagram, what are the directions of the spinning object’s velocity and centripetal force

• The velocity is tangential to the path, and the centripetal force is directed towards the center.

• The velocity is directed towards the center, and the centripetal force is tangential to the path.

• Both the velocity and the centripetal force are directed towards the center.

• Both the velocity and the centripetal force are tangential to the path.

Two factors that influence the force of gravity: 1. 2.

• Mass and distance

• Temperature and pressure

• Speed and velocity

• Time and space

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What is the centripetal force that keeps planets in our solar system in orbit around the sun?

• Gravitational force

• Magnetic force

• Electromagnetic force

• Nuclear force

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Kepler’s first law states that the orbit of a planet is:

• a perfect circle

• an ellipse with the Sun at one of the two foci

• a straight line

• a spiral

Kepler’s second law states that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.

• Kepler’s first law

• Kepler’s second law

• Kepler’s third law

• Newton’s law of universal gravitation

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What is Kepler’s third law?

• Kepler's third law states that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

• Kepler's third law states that planets move in elliptical orbits with the Sun at one focus.

• Kepler's third law states that the line joining a planet and the Sun sweeps out equal areas during equal intervals of time.

• Kepler's third law states that the force between two objects is proportional to the product of their masses and inversely proportional to the square of the distance between them.

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