Circular Motion Quiz

Circular Motion

• On a merry-go-round, horses near the outside move faster than those near the center due to greater linear speed.
• The linear speed of a horse increases as its distance from the center of the merry-go-round increases.
• If a turntable's rotational speed is doubled, the linear speed of a pet hamster sitting on the edge of the record will also double.
• If the hamster moves to a point twice as far from the center of the record player, its linear speed will also double.
• On a curved railroad track, the outer track is longer, so the wheel on the outer track needs to roll faster than the wheel on the inner track to cover the same distance.
• A tapered wheel rim on a train allows it to cover different distances per revolution on a curved track.
• The narrow part of a tapered wheel on a railroad train has a lower tangential speed compared to the wide part.

Circular Motion

• The linear speed of an object in circular motion is proportional to its rotational speed and radius.
• Objects at different distances from the center of circular motion can have different linear speeds.
• The circumference of a bicycle wheel is 2 meters, and if it rotates at 1 revolution per second, its linear speed is 2 m/s.
• A rock at the middle of a spinning string moves half as fast as a rock at the end of the string.

Force and Circular Motion

• The net force exerted on a car traveling in a circular path at constant speed is directed toward the center of the curve.
• 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 62.8 m/min.

Rotational Inertia

• The rotational inertia of an object is greater when it is not symmetrical or when its mass is farther from the axis of rotation.
• A leg has a greater rotational inertia when it is straight.
• You can swing your legs to and fro more frequently when your legs are bent.

Centripetal and Centrifugal Force

• Centrifugal forces are an apparent reality to observers in a rotating reference frame.
• The force responsible for a car moving steadily along a no-friction icy banked curve is due to the radial component of the normal force.
• Centripetal force does no work on a circularly-moving object because it has no component in the direction of motion.
• A conical pendulum swings in a circular path.

Angular Momentum

• Angular momentum involves radial distance and two types of speed.
• Multiplying the equation for linear momentum by radial distance r gives angular momentum.
• The gravitational field simulated by rotation in a space habitat that is best suited for humans is in a sphere.

Rotational Inertia and Real-World Applications

• Attaching a heavy glob of clay to the upper end of a meterstick increases the time it takes to fall when rotated.
• A vertically-held sledge hammer is easier to balance when the heavier end is at the top, away from your hand.
• A broom stands upright longer when the bristles end is on the floor.
• A filled jar rolls down an incline in a shorter time than an empty one.
• A tin can filled with water rolls down an incline in a shorter time than one filled with ice.

Torque

• Torque involves rotation, leverage, and distance from an axis of rotation.
• A torque acting on an object tends to produce rotation.