Physical Science 8th grade (1).pdf

Physics tells us that if something is rotating it

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Physics tells us that if something is rotating, it will continue to rotate unless a twisting force stops it from rotating. The same also holds true if something is not rotating. It will need a twisting force to start it rotating. Skateboarders use their arms to create this twisting force. Also known as torque, this twisting force allows the skateboarder to turn around in mid- air. By pulling their arms in as they twist them, skateboarders create torque. That’s how they seem to defy gravity in a successful frontside 180. The evolution of skateboarding will continue to change with each new generation. Skating stunts and styles will change dramatically, but the science will remain the same. Questions: 1. Do skateboarders actually defy the laws of physics? Why or why not? 2. How does "pumping" increase a skater’s acceleration? 3. What is torque and how does a skateboarder use it? Chapter 14 Connection
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306 Making a Spool Car Newton’s three laws can be used to explain the motion of everyday objects: from a car driving down the highway to the moon orbiting around Earth. The first law says that objects at rest tend to stay at rest and objects in motion tend to stay in motion with constant speed and direction. The second law explains the relationship between force and acceleration ( a = F / m ). According to the third law, an action created by one object results in an equal but opposite reaction on another object. In this activity you will build a car and apply Newton’s laws to explain how it works and why it moves as it does. Materials: Thread spool, assorted rubber bands, approximately 2-3 cm long, metal washer - approximately 2 cm in diameter, piece of masking tape, pencil, paper clip, carpeted floor, rug, or fabric on which to run the car What you will do 1. Attach a rubber band to the paper clip. 2. Slide the paper clip partially through the center of the spool, leaving the rubber band exposed at one end. 3. Place the washer over the rubber band and slide a pencil through the loop. 4. Push the paper clip through to the other end of the spool. 5. Adjust the paper clip so it lies flat against the spool and holds the rubber band in place. Use a piece of tape to secure it. 6. Turn the pencil several times to twist the rubber band. Place the car on the carpeted floor and release it. 7. Experiment with the car until you can get it to move in a straight line. Adjusting the position of the pencil may be helpful. 8. Determine the number of turns of the pencil that gives the greatest distance of travel. 9. If time allows, experiment with other rubber bands until you have made a spool car that goes as far and as straight as possible. Race your car against your classmates to determine who has the best car. 10.Try to run your car on a smooth floor and observe what happens.
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