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I challenge

I challenge. Slip and slide. I Challenge. Each year my family has a slip and slide challenge between the members of our family. This year I really want a member of my family take home the fastest slider trophy, as well as the Speedy brick Trophy

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I challenge

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  1. I challenge Slip and slide

  2. I Challenge • Each year my family has a slip and slide challenge between the members of our family. This year I really want a member of my family take home the fastest slider trophy, as well as the Speedy brick Trophy • I am challenging the class to help me identify what factors I should consider when preparing my family members for the competition.

  3. Slip and Slide • Videos: • http://www.youtube.com/watch?v=ho-UTvQmoDg • http://www.youtube.com/watch?v=a_jwX86FpeI&feature=related • http://www.youtube.com/watch?v=w6Goz5Ngchg&NR=1&feature=fvwp

  4. The two questions • How does the mass of an object affect the motion of an object as it moves across a table top? • How does the material of a surface affect the motion of an object as it moves across a table top?

  5. Materials • Dynamics box • String • Triple beam balance • hangar • Pulley • Set of masses (question 1) • Four surfaces, table top, two different wood boards, and white boards. • Motion detector

  6. Share Data Tables from Question 1 Groups

  7. What conclusions can we draw from the data taken by the groups investigating Question #1 • Student Responses

  8. Data table Question 2

  9. Share Data Tables from Question 2 Groups

  10. What conclusions can we draw from the data taken by the groups investigating Question #2 • Student Responses

  11. Exit Ticket • In order for my family to take home a slip and slide trophy what suggestions can you make to each of us to increase our chances. Question 1: Which family member has the best chance according to their masses to win? • Anthony mass 13 kg • Sophia mass 16 kg • Cristina mass 56 kg • David mass 99 kg Question 2: The family member with the largest mass is allowed to pick from one of the following in order to decrease their time down the slide; change the fluid from water to pancake syrup, change the water flow from low to high, change the fluid from water to vegetable oil. Choose one option and explain how it will increase their change to win the Speedy Brick Trophy.

  12. Friction Cornell Notes

  13. Objects at Rest • What does Newton’s First law say about this object’s motion? • What is the net force acting on this object at rest? • What does Newton’s Second Law tell us about changing this object’s Motion so that it is now accelerating? • What limits the objects motion and causes the object to seem to ignore the First Law?

  14. Friction • Friction opposes the applied force. • When friction and applied force are equal they are in equilibrium and the object is either at rest or moving with a constant velocity.

  15. Friction is the force exerted by a surface as an object moves across it or makes an effort to move across it. • View animation and demos. • Red truck. • Race Track 4. For our purposes we will study two types of friction: A. Static friction (starts to move or at rest) B. Kinetic friction (moving)

  16. Static Friction • Static friction is the force that resists the initiation of sliding motion between two surfaces that are in contact and at rest. • Static Friction: • To move an object the force applied needs to be greater than static friction • All surfaces have a coefficient of static friction based on the roughness of surface.(μs) • It typically takes more force to budge an object into motion than it does to maintain the motion once it has been started.

  17. Kinetic Friction • Kinetic Friction is the force that opposes the movement of two surfaces that are in contact and are sliding over each other. • Kinetic Friction: a. The object is moving. b. The coefficient of friction is dependent upon the surfaces, μk. c. The values of friction provide a measure of the relative amount of adhesion or attraction of the two surfaces for each other.

  18. 9. What does Friction Depend on? • Discuss results from Slip and slide • More examples • Derivation Fn Fapp Ff Fg=W=mg

  19. Application: Balanced forces 10. When the forces are balanced the sum of the forces is equal to zero, ΣF=0. 11. The object will be at rest or moving with a constant velocity.

  20. 12. Static Application ΣF=0 Scenario. A 5 kg book is at rest on a table an applied force of 15 N to the right causes the book to start to move. • Read the scenario and label the forces on the free body diagram. See board. • Next we will sum up all the forces involved in the motion across the table and set them equal to zero. • Substitute known values and solve for μs.

  21. 13. Kinetic Application ΣF=0 Scenario. A 5 kg book is moving across a table with a constant velocity and an applied force of 10 N to the right. • Read the scenario and label the forces on the free body diagram. See board. • Next we will sum up all the forces involved in the motion across the table and set them equal to zero. • Substitute known values and solve for μk.

  22. Kinetic Friction and AccelerationForces not balanced 14. If the object in the scenarios for 12 and 13 where now accelerating the ΣF=ma. 15. Scenario: A 5 kg book has an applied force of 20 N applied that causes the book to accelerate to the right. The coefficient of kinetic friction is 0.204. Calculate the acceleration. • Read the scenario and label the forces on the free body diagram. See board. • Next we will sum up all the forces involved in the motion across the table and set them equal to ma • Substitute known values and solve for acceleration.

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