Circular Motion Autumn, Chiara, Maddie, Joe, Keaton

State and Explain Major Concepts An axis is the straight line about which rotation takes place. When the axis is located within the body, the motion is called a rotation, or a spin. When an object turns about an external axis, the rotational motion is called a revolution. Linear speed is what we have been calling simply "speed" - the distance in meters or kilometers moved per until of time. Rotational speed refers to the number of rotations or revolutions per unit of time. Any force that causes an object to follow a circular path is called a centripetal force. Centripetal means "center-seeking," or "toward the center." Sometimes however, an outward force is attributed to circular motion. This outward force is called centrifugal force. Centrifugal means "center-fleeing," or "away from the center."

Historical Perspective Although Galileo and Decartes were involved, in a vague way, with the study of circular motion, the real study of the subject is accredited to Christian Huygens. With his extensive study of the motion of various objects, he was able to develop the law of centripetal acceleration and uniform circular motion. His findings aided Newton in further discoveries involving circular motion.

Application of Concepts Circular motion is common to almost all sports. It could be car racing, track and field, baseball, running or ice-skating and a lot more because the motion of objects in circles is a common observation of sports viewers around the world. Like any object moving in a circle, the motion of these objects that we see are governed by Newton's laws of motion. Their circular motion - however brief or prolonged they may be - is characterized by an inward acceleration and caused by an inward net force. The most common example of the physics of circular motion in sports involves the turn. It could be a halfback in football making a turn around the corner of the line, but it could also be a softball player running the bases and making a turn around second base. Other examples of application of circulars motion could be a marry-go- round, or a satellite orbiting the Earth

Review Questions 1. A rotation is a spin where the axis is located within the body, a revolution is when an object turns around an external axis. 2. A child on a merry-go-round revolves around the merry-go-rounds axis 3. Linear speed is distance in meters or kilometers moved per unit of time, rotational speed is the number of rotations per unit of time. 4. Linear speed is directly related to rotational speed. Linear speed depends on the distance from the center of the rotating platform 5.The direction of the force acting on the can is towards the center of the circle. 6. The force that holds the rider on the carnival ride acts toward the center 7. Outward force 8.Centripetal force 9. No force acts on the can 10.The can being whirled around and pushes on the ladybugs feet and provides the centripetal force that keeps the ladybug on the circular path. The ladybug in turn presses against the can. 11. I cannot name the action and reaction forces in which one force is the centrifugal force acting on an empty can swung in a circle, because the centrifugal force is a fictitious force. 12.Centrifugal force in a rotating frame is considered fictitious because nothing produces it, it is a result of rotation. 13. Gravity can be simulated in an orbiting space station that is 2km in diameter by rotating it at a speed of one rotation per minute. 14. The orbiting space station would have to be a large structure so it could rotate slowly so the people on the space station wont get dizzy. 15. If the values of g at the inside outer edge would be 1, and halfway to the axis would be 0.5, and at the axis itself it would be 0.

Think and Explain Questions 1. If a ladybug sits halfway between the axis and the edge of a turning record and the rpm doubles the linear speed will also double, if the ladybug was moved to the edge of the record that would also double the linear speed, if the ladybug was moved to the edge and the rpm of the record was doubled the lienar speed would be quadrupled. 2. If you fell off the edge of a rotating merry-go-round your path would be a tangent line to the merry-go- round. 3. A motorcycle can ride on the vertical wall of a bowl-shaped track because of the centrifugal force. 4. When a gliding seagull suddenly turns in flight the source of the centripetal force acting on it is the wind on its wings. 5. Centripetal force does not act on a rotating object because there isn't a a force acting at a right angle to the path of the rotating object. 7. If a rotating space station rotates at a speed that gives the inhabitants 1 g of acceleration was made to rotate faster the acceleration will be greater than 1 g. 8. People on earth would weigh less if the rotation was faster because the earth rotates and the centrifugal force would pull them out and away from the earth, however people on a rotating space station would weigh more with an increased spin speed because they stand on the inside outer rim so the centrifugal force would be pulling them against the floor. 9. If a man were in a rotating sphere of that was 4m in diameter and he was 2 m tall where his feet are in 1 g the acceleration at his head would be 0.5 g. 10. Two space crafts with long cables would be able to attach the space crafts to a giant asteroid on either side of it with the cables then move in two opposite directions to cause rotation and produce 1 g of acceleration.

Framing the Demonstration Background Information or initial observations An axis is the straight line about which rotation takes place. When the axis is located within the body, the motion is called a rotation, or a spin. When an object turns about an external axis, the rotational motion is called a revolution. Linear speed is what we have been calling simply "speed" - the distance in meters or kilometers moved per until of time. Rotational speed refers to the number of rotations or revolutions per unit of time. Any force that causes an object to follow a circular path is called a centripetal force. Centripetal means "center-seeking," or "toward the center." Sometimes however, an outward force is attributed to circular motion. This outward force is called centrifugal force. Centrifugal means "center-fleeing," or "away from the center."

Question or Hypothesis Question: How does weight affect the circular path of a stopper? Hypothesis: I hypothesize that the less weight we add, the more times it will turn because it will be lighter.

Step by Step 1. First we will record the mass of one washer and the mass of one stopper as well as the length of the string. 2. Then we will start with 2 washers on the string and see how many times a circle is made once the person spinning the string stops. 3. Record the number of revolutions made. 4. Now do the same thing with 4 washers, 8 washers and 12 washers.

General Statement for conducting the experiment We will add weight to a string by adding washers to it to determine how weight affects how many times a revoluton is made.

Materials Needed 12 washers grams each 1 stopper grams each glass cylinder tube string cm radius cm

Safety Precautions 1. Make sure the rotating stopper does not hit anyone in the head 2. Don’t cut yourself on glass if broken 3. Don't let the washers fly off and hit you

Collecting and Presenting Data Number of Washers Mass of Washers Number of Rotations Trial One: g 21 Trial Two: g 6 Trial Three: g 3 Trial Four: g 3

Analyzing and Interpreting Results The centriful force of the stopper lifted the weight on the other end of the string. The more weight that was on the string the less rotations the stopper made when force was no longer applied to the system.

Conclusions The centriful force that was produced by the circular motion of the stopper lifted the weights, but applying more weight for the stopper to lift decreased the number of rotations that the weight was held up. Our hypothesis that the less weight we add, the more times it will turn because it will be lighter was correct