BEST PRACTICE on Uniform Circular Motion

A force F moves an object of mass m in a circle of radius r at a speed v. How much force would be needed if the mass is doubled, but all other quantities are the same?

• F

• 2F

• F/2

• 4F

An object of mass m moves in a circle of radius r at a constant speed v. What is the effect to the speed and acceleration if the radius is doubled, but all other quantities are the same?

• Both speed and acceleration double.

• Both speed and acceleration are halved.

• The speed is doubled but the acceleration is halved.

• The speed is halved but the acceleration is doubled.

An object of mass m moves in a circle of radius r at a constant speed v and acceleration a. If the period is doubled, but all other quantities are the same, what is the new acceleration?

• 2a

• a/2

• a/4

• 4a

A runner moving at a speed of 8.8 m/s rounds a bend with a radius of 25 m. What is the centripetal acceleration (in m/s²) of the runner? Express the answer in 2 significant figures. No need to write the units.

A race car of mas 600 kg rounds a flat curve of 56 m in radius at 32 m/s . What minimum static friction between the tires and road would be needed for the car to round the curve without slipping?

• 11 kN

• 0.34 kN

• 59 kN

• 1.1 kN

A 615-kg racing car completes one lap in 14.3 s around a circular track with

a radius of 50.0 m. The car moves at constant speed. What is the acceleration of the car in m/s²? Express the answer in 3 significant figures. No need to write the units.

An athlete whirls a 7.00-kg hammer tied to the end of a 1.30-m chain in a

horizontal circle. The hammer makes one revolution in 1.00 s. What is the tension (in newtons) in the chain? Express the answer in 3 significant figures. No need to write the unit.

A vinyl stereo record is making 33 1/3 revolutions per minute. What is its period in seconds? Express the answer in 1 decimal place. No need to write the unit.

A coin is placed on a vinyl stereo record with a period of 1.50 s. Find the magnitude of the acceleration when the coin is placed 15.0 cm from the center of the record.

• 2.63 m/s²

• 0.838 m/s²

• 395 m/s²

• 263 m/s²

What is the maximum speed (in m/s) at which a car can safely travel if the radius

of the track is 80.0 m and the coefficient of friction is 0.40? Round the answer off to a whole number. No need to write the units.