Circular Motion and Newton's Law of Universal Gravitation

The velocity vector of an object in uniform circular motion points:

• to the center of the circle.

• tangent to the circle (along the outside of it).

• out of the circle.

• Velocity is not a vector and does not have a direction.

When an object moves in uniform circular motion, the direction of its acceleration is

• in the same direction as its velocity vector.

• in the opposite direction of its velocity vector.

• directed toward the center of its circular path.

• directed away from the center of its circular path.

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it

• moves along a straight-line path away from the center of the circle.

• moves along a straight-line path toward the center of the circle.

• moves along a straight-line path in its original direction.

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When a car goes around a circular curve on a horizontal (unbanked) road at constant speed, what force causes it to follow the circular path?

• the normal force from the road

• the friction force from the road

• gravity

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Two cars go around a banked curve at the proper speed for the banking angle. One car has tires with excellent traction, while the other car has bald slippery tires. Which of these cars will probably slide on the pavement as it goes around the curve?

• The car with excellent traction

• The car with bald slippery tires

• Both cars will slide

• Neither car will slide

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If Earth had twice its present mass but orbited at the same distance from the sun as it does now, its orbital period would still be 1 year. Explain why the period would not change. (Hint: Earth is the satellite in this case.)

A 150-g ball at the end of a string revolves uniformly in a horizontal circle of radius 0.600 m. The ball makes 2.00 revolutions per second (T=0.500s). What is its centripetal acceleration (a_c)?

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A child with a mass of 22.5 kg is sitting 1.20m from the center of a merry-go-round and moving with a speed of 1.10 m/s. Calculate the centripetal acceleration (aₐ) of the child.

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A child with a mass of 22.5 kg is sitting 1.20m from the center of a merry-go-round and moving with a speed of 1.10 m/s. Calculate the net horizontal force (Fₙₑₜ) exerted on the child.

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A geosynchronous satellite orbiting at a height of 36,000 km above the Earth’s surface. What is the speed of the satellite in m/s (meters per second)?

• 7000 m/s

• 7800 m/s

• 8000 m/s

• 8800 m/s

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