Lecture 5; circular motion

The circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second then its linear speed is: A. 2 m/s. B. 3 m/s. C. 6.28 m/s. D. 3.14 m/s. E. 1 m/s.

A. 2 m/s.

Two cars are traveling at the same constant speed v. As the drawing indicates, car A is moving along a straight section of the road, while car B is rounding a circular turn. Which statement is true about the accelerations of the cars? A. Car A is not accelerating, but car B is accelerating. B. Car A is accelerating, but car B is not accelerating. C. The acceleration of both cars is zero, since they are traveling at a constant speed. D. Both cars are accelerating.

A. Car A is not accelerating, but car B is accelerating.

Two cars are driving at the same constant speed v around a racetrack. However, they are traveling through turns that have different radii, as shown in the drawing. Which statement is true about the magnitude of the centripetal acceleration of each car? A. The magnitude of the centripetal acceleration of the car at A is greater than that of the car at B, since the radius of the circular track is smaller at A. B. The magnitude of the centripetal acceleration of the car at A is greater than that of the car at B, since the radius of the circular track is greater at A. C. The magnitude of the centripetal acceleration of each car is the same, since the cars are moving at the same speed. D. The magnitude of the centripetal acceleration of the car at A is less than that of the car at B, since the radius of the circular track is smaller at A.

A. The magnitude of the centripetal acceleration of the car at A is greater than that of the car at B, since the radius of the circular track is smaller at A.

A motorcycle travels at a constant speed around a circular track. Which one of the following statements about this motorcycle is true? A. The velocity of the motorcycle is changing. B. The motorcycle is characterized by constant acceleration. C. The motorcycle is characterized by constant velocity. D. The motorcycle has a velocity vector that points along the radius of the circle. E. The motorcycle has an acceleration vector that is tangent to the circle at all times.

A. The velocity of the motorcycle is changing.

For the ball on the end of a string moving in a vertical circle: What is the direction of the net force on the ball? A. toward the center of the circle B. tangent to the circle C. there is no net force

A. toward the center of the circle

An Earth satellite needs to have its orbit changed so the new orbit will be twice as far from the center of Earth as the original orbit. The new orbital period will be twice as long as the original period. A. True B. False

B. False

If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out because an outward force balances the pull of gravity on the water. A. True B. False

B. False

Orbiting satellites accelerate toward Earth at 9.8 m/s2. A. True B. False

B. False

Satellites in circular orbits around Earth are in equilibrium because they have uniform speed. A. True B. False

B. False

Satellites in orbit are accelerated toward Earth, so they must be getting closer and closer to our planet. A. True B. False

B. False

If an object is moving in uniform circular motion, its period is determined by which one of the following quantities? A. the speed of the object B. the time interval for the object to make one revolution C. the number of revolutions the object makes each second D. the centripetal acceleration of the object E. the displacement of the object

B. The time interval for the object to make one revolution.

The net force exerted on a car traveling in a circular path at constant speed is: A. zero because the car is not accelerating. B. directed forward, in the direction of travel. C. directed toward the center of the curve.

C. directed toward the center of the curve.

For uniform circular motion, the acceleration: A. is larger for a larger orbit at the same speed. B. is always due to gravity. C. is directed toward the center of the circle. D. is parallel to the velocity. E. is always negative.

C. is directed toward the center of the circle.

When the ball reaches the break in the circle, which path will it follow?

C. straight up.

When a ball on the end of a string is swung in a vertical circle, the ball is accelerating because: A. the speed and the direction are changing. B. the ball is not accelerating. C. the direction is changing. D. the speed is changing.

C. the direction is changing.

If you're on a Ferris wheel at a carnival, seated 10 m from the Ferris wheel's axis that makes a complete rotation each minute, your linear speed is: A. 100 m/min. B. 31.4 m/min. C. 10 m/min. D. 62.8 m/min. E. need more information

D. 62.8 m/min

The centripetal force is best explained by which of the following statements? A. The centripetal force is the force on an orbiting object that is directed along a line that is tangent to the circle. B. The centripetal force is the force on an object that is directed radially outward from the center of its orbit. C. The centripetal force is a fundamental force of nature. D. The centripetal force is the net force acting on an orbiting object that maintains it in uniform circular motion.

D. The centripetal force is the net force acting on an orbiting object that maintains it in uniform circular motion

A bicycle racer is traveling at constant speed v around a circular track. The centripetal acceleration of the bicycle is ac. What happens to the centripetal acceleration of the bicycle if the speed is doubled to 2v? A. The centripetal acceleration does not change. B. The centripetal acceleration increases to 2ac. C. The centripetal acceleration decreases to 0.25 ac. D. The centripetal acceleration decreases to 0.5ac. E. The centripetal acceleration increases to 4ac.

E. The centripetal acceleration increases to 4ac.

A satellite orbits the Earth in uniform circular motion. What is the direction of centripetal acceleration of the satellite? A. The centripetal acceleration vector points in the direction opposite that of the satellite's velocity. B. The centripetal acceleration vector points radially outward from the Earth. C. The centripetal acceleration vector points in the direction of the satellite's velocity. D. Because the centripetal acceleration is a scalar quantity, it doesn't have a direction. E. The centripetal acceleration vector points radially inward toward the Earth.

E. The centripetal acceleration vector points radially inward toward the Earth.

When using the term "uniform circular motion", what do we mean by the term "uniform"? A. The motion occurs without the influence of the gravitational force. B. The motion occurs without the influence of the gravitational force. C. The motion of the object is at a constant speed. D. The forces acting on the object are uniformly applied from all directions. E. The motion of the object is at a constant speed.

E. The motion of the object is at a constant speed.