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Weight, Mass & Friction: Understanding Physics Concepts through Fun Scenarios

Explore weight, mass, and friction concepts through engaging scenarios like alien encounters and gravitational differences on planets. Learn Newton's laws with practical examples and solve physics problems to enhance your understanding. Discover the types of friction and how surface area, mass, and texture affect it. Have fun while mastering physics with interactive challenges and experiments.

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Weight, Mass & Friction: Understanding Physics Concepts through Fun Scenarios

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  1. Warmup Sept 17th - Think • You were kidnapped and knocked out. Some time later, you wake up in a dark warehouse. All there is in the room is a scale and a light, so you decide to weigh yourself. WOW!!! You gained a whole lot of weight last night…what happened? • You remember seeing alien figures in a dream-state, and realize you must be on another planet. Is the planet smaller or more massive than Earth?

  2. Weight and Mass… Fg = mg (formula for weight) Fg (weight) is the force an object has due to gravity Gravity on the Earth 9.8m/s2

  3. Weight and Mass… What’s the mass of my 893N ex-husband that just happens to be in my basement?

  4. Weight Problems! Fg=mg • What does a 60kg tool weigh? • What’s the mass of a crate of tools that weighs 234 N?

  5. Weight and mass: • What does a case of the new Chipotle Gatorade with a mass of 54.8kg weigh?

  6. What would a 60kg tool weigh: • On Mars (accel of gravity 3.7m/s2 )? • On Jupiter (accel of gravity 24.8m/s2 )?

  7. What planet are you on?You have a 4kg cat that weighs 14.4N

  8. Now it’s time for Newton’s 2nd Law • Newton’s 1st: Inertia. At rest, stay at rest; in motion, stay in motion. • Newton’s 2nd: What happens when a force acts on an object? • Acceleration.

  9. Newton’s Second Law:Force = mass x acceleration Force equals mass times acceleration. F=ma

  10. Newton’s Second Law: • The acceleration of an object is directly proportional to the force applied to the object, and inversely proportional to the mass. • -or – if F then A if M then A

  11. Calculate the Force How Do We?

  12. How? Like this: My 4 kg cat, Jeter, ran at our kitten Shadow with an acceleration of 3.0 m/s2. He didn’t stop. Poor little kitten! After suffering a mild concussion, we wondered….how much force did Jeter hit him with? Force = mass x acceleration, or… 4 x 3 = 12

  13. 12 what? Remember Force has its own special unit… 1kg x 1m/s2 = 1 newton (1N) F = ma Learn it. Live it. Love it.

  14. Force = mass(acceleration) 1. How much force is needed to push a lawnmower of 30 kg at 2.5 m/s2?

  15. 2. How much force must be applied to a bowling ball that has a mass of 5kg to achieve an acceleration of 25m/s2?

  16. 3. What is the mass of a baseball that has an acceleration of 125 m/s2 after a force of 44 Newtons has hit it?

  17. 4. What is the acceleration of a 22kg wolf that hits attacks a bear with a force of 400 Newtons?

  18. Now you practice!

  19. Without friction…

  20. FRICTION Friction - a force that opposes motion, or “pushes back” when two surfaces are touching. It’s always around and it affects everything.

  21. Without friction…

  22. FRICTION- works against you …..but it can be helpful! When do I want… • A lot of friction? • http://www.youtube.com/watch?v=yTKwS-J7qVE • A little bit of friction? • http://digg.com/video/the-science-of-figure-skating • http://www.nbclearn.com/olympics

  23. Friction types and parts… • There are three Basic Types of Friction • Static • Kinetic • Fluid

  24. Types of friction: 1) Static friction: Friction that resists the start of sliding motion between two objects at rest. Keeps things stopped

  25. Types of friction: 2) Kinetic friction: The force that opposes the movement of two surfaces that are in contact and moving over each other.To make something move, you just overcome static friction by pulling with a force larger than kinetic friction.

  26. Kinetic Friction: Sliding or Rolling

  27. Types of friction: 3) Fluid friction: The friction between layers of a fluid. 2 types- Liquid and Gas Liquid- water, oil etc. Gas - Air

  28. Types of friction: Described by viscosity. Viscosity – the “thickness” of a fluid. Low viscosity = “thin;” High viscosity = “thick” or “viscous.” The less viscous a fluid is, the easier it moves.

  29. Does Size Matter? I’m talking about Mass or surface area folks!

  30. Friction DOES depend upon: • 1. surface area in contact • 2. mass/gravity (weight) of object • 3. the texture of the surface

  31. Friction is cumulative • Small amounts of friction in a system add up to become a large amount of friction.

  32. Textbook friction…CHALLENGE

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