Circular Motion Review

An object, shown in the accompanying figure, moves in uniform circular motion. Which arrow best depicts the net force acting on the object at the instant shown?

• A) A

• B) B

• C) C

• D) D

• E) None

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An object, shown in the accompanying figure, moves in uniform circular motion. Which arrow best depicts the direction of the velocity of the object at the instant shown?

• A) A

• B) B

• C) C

• D) D

• E) None

A car moves along the curved track. What is the apparent weight of the driver when the car reaches the lowest point of the curve? (Remember Fc = ma)

• A) mg

• B) mg + ma

• C) ma – mg

• D) mg/ma

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A 0.2 kg ball rotates at a constant speed of 3 m/s on the end of 1.2 m long string. The string describes a horizontal circle. What is the centripetal acceleration of the object?

• 1.2 m/s^2

• 3.0 m/s^2

• 7.5 m/s^2

• 3.2 m/s^2

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A 0.2 kg ball rotates at a constant speed of 3 m/s on the end of 1.2 m long string. The string describes a horizontal circle. What is the centripetal force exerted on the object?

• 1.0 N

• 1.2 N

• 0.2 N

• 1.5 N

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NGSS.HS-PS2-1

A child whirls a ball at the end of a rope, in a uniform circular motion. Which of the following statements is NOT true?

• The speed of the ball is constant.

• The velocity of the ball is constant.

• The radius is constant

• The magnitude of the ball's acceleration is constant.

A centripetal force F is applied to an object moving at a constant speed v in a horizontal circle of radius r. If the radius is quadrupled and the speed is doubled, what happens to the centripetal force?

• Increased by a factor of 2

• Decreased by a factor of 2

• Doesn't change

• Increased by a factor of √2

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NGSS.HS-PS2-1

A heavy (2.0 kg) point-like object rests 2.0 m from the center of a rough turntable as the turntable rotates. The period of the turntable's rotation is 5.0 seconds. The coefficient of kinetic friction between the object and turntable is 0.15, while the coefficient of static friction is 0.32. What is the closest value for the magnitude of the force of friction acting on the object?

• 19.6N

• 16.0N

• 9.8N

• 6.4N

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NGSS.HS-PS2-1

What is the centripetal acceleration of an object (mass = 50 g) on the end of an 80-cm string rotating at a constant rate of 4 times a second?

• 25 m/s^2

• 32 m/s^2

• 100 m/s^2

• 500 m/s^2

• 2500 m/s^2

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NGSS.HS-PS2-1

Riders in a carnival ride stand with their backs against the wall of a circular room of diameter 8.0 m. The room is spinning horizontally about an axis through its center at a rate of 45 rev/min when the floor drops so that it no longer provides any support for the riders. What is the minimum coefficient of static friction between the wall and a 75 kg rider required so that the rider does not slide down the wall?

• 0.0012

• 0.056

• 0.11

• 0.53

• 8.9

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