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Chapter 4

Chapter 4. 4.1. Force- push or pull Contact- Example: Field- Example:. Agent- whatever is causing the force Example:. System- object that the force acts upon Example:. Free Body Diagram. Draw the system/agent Label the forces Choose a direction to be positive

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Chapter 4

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  1. Chapter 4

  2. 4.1

  3. Force- push or pull • Contact- • Example: • Field- • Example:

  4. Agent- whatever is causing the force • Example: • System- object that the force acts upon • Example:

  5. Free Body Diagram • Draw the system/agent • Label the forces • Choose a direction to be positive • Draw arrows to represent the magnitude of the force

  6. Types of Forces

  7. A football is moving upwards towards its peak after having been booted by the punter. Diagram the forces acting upon the football as it rises upward towards its peak

  8. Newton’s 1st Law • An object at rest will remain at rest and an object that is moving will continue to move in a straight line with constant speed, if and only if the net force acting on that object is zero

  9. Inertia- tendency of an object to resist change • Examples: • Demos: 1 point Extra Credit! • Must be done in class as a presentation! • Cannot be any that Mrs. Sturgeon has shown in class!

  10. Combining Forces • Net Force- Overall Force of a system • Forces can be combined/subtracted like other vectors

  11. Equilibrium- Net force equals zero • What will the velocity be at equilibrium?____

  12. Deriving a=F/m • If you keep the length of the rubber band the same over time the cart will accelerate w/ a constant rate

  13. The more carts the more force needed to keep the same acceleration • Slope=1/mass so we see a=Force/mass

  14. Deriving Work

  15. Force=1kg m/s2=Newton

  16. 4.2 • Newton’s 2nd Law • Force=acceleration x mass • In Freefall: Fg=mg • On a Scale: Fsp=FgNet Force=zero • Weight’s unit is _________

  17. Apparent Weight- the force an object experiences as a result of all the forces acting on it, giving the object acceleration • What would happen to your weight if you were on an elevator • Going up? • Going down?

  18. Weightlessness- does not mean an object’s weight is zero, but there are no contact forces

  19. Drag Forces- force exerted by a fluid (air) on an object, the properties of the object, and the properties of the fluid that the object is moving through • Speed • Viscosity • Temperature

  20. Terminal Velocity- constant velocity that is reached when drag force equals the force of gravity

  21. 4.3- Interaction Forces • Force is the result of an interaction between two objects • Forces always come in pairs

  22. Interaction pair- 2 forces that are in opposite directions and have equal magnitude • AKA- action-reaction pairs of forces

  23. Newton’s 3rd Law of Motion • All forces come in pairs and they are equal in strength and opposite in direction • Examples:

  24. Forces of Ropes and Strings • Tension- specific name for the force exerted by a string or rope • The tension of the rope is the weight of all objects below it

  25. Tug of War • If both sides are pulling with 500 N: • What is the Net Force? • What is the tension of the rope?

  26. Normal Force • Normal force- the perpendicular contact force exerted by a surface on another object • FN=Fg

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