Chapter 7 Physics

When an object is moving with uniform circular motion, the object’s tangential speed

• is circular.

• is perpendicular to the plane of motion.

• is constant.

• is directed toward the center of motion.

The centripetal force on an object in circular motion is

• in the same direction as the tangential speed.

• in the direction opposite the tangential speed.

• in the same direction as the centripetal acceleration.

• in the direction opposite the centripetal acceleration.

A ball is whirled on a string, then the string breaks. What causes the ball to move off in a straight line?

• centripetal acceleration

• centripetal force

• centrifugal force

• inertia

If you lift an apple from the ground to some point above the ground, the gravitational potential energy in the system increases. This potential energy is stored in

• the apple.

• Earth.

• both the apple and Earth.

• the gravitational field between Earth and the apple.

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When calculating the gravitational force between two extended bodies, you should measure the distance

• from the closest points on each body.

• from the most distant points on each body.

• from the center of each body.

• from the center of one body to the closest point on the other body.

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The gravitational force between two masses is 72 N. What is the gravitational force if the distance between them is tripled?

(G = 6.673 x 10^–11 N•m²/kg²)

• 8.0 N

• 9.0 N

• 36 N

• 54 N

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In the figure, according to Kepler’s laws of planetary motion,

• A₁ = A₂.

• Δt₁ > Δt₂.

• if Δt₁ = Δt₂, then the orbit is circular.

• if Δt₁ = Δt₂, then A₁ = A₂.

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Newton’s law of universal gravitation

• can be derived from Kepler’s laws of planetary motion.

• can be used to derive Kepler’s third law of planetary motion.

• can be used to disprove Kepler’s laws of planetary motion.

• does not apply to Kepler’s laws of planetary motion.

• the mass of the sun

• the mass of Earth

• the mass of the central object

• the mass of the orbiting object

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How would the speed of Earth’s orbit around the sun change if Earth’s mass increased by 16 times?

• It would increase by a factor of 2.

• It would increase by a factor of 4.

• It would decrease by a factor of 2.

• The speed would not change.

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