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Physical Science

Physical Science. Chapter 12 Forces and Motion. Forces and Motion. What is a Force? A Force is a Push or Pull Exerted on an Object. Forces cause Objects to Speed up, Slow down, or Change Direction as they Move. A Force Exerted on an Object Causes that Object’s Velocity to Change; that is,

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Physical Science

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  1. Physical Science Chapter 12 Forces and Motion

  2. Forces and Motion • What is a Force? • A Force is a Push or Pull Exerted on an Object. • Forces cause Objects to Speed up, Slow down, or Change Direction as they Move. • A Force Exerted on an Object Causes that Object’s Velocity to Change; that is, All Forces Cause an Acceleration

  3. Forces and Motion • How can you cause an object to move? • Push on it or pull on it. • Push harder on an object and you have a greater effect on its motion. • If you push the book to the right, the book moves towards right.

  4. Forces and Motion • Force is a Vector • The Final Force is the Net (Sum) of the Total Forces on an Object • If the Final Force on an Object DOES NOT = 0, the Object Is Accelerating

  5. Forces and Motion • Combining Forces • Forces are Vectors • They May Strengthen Each Other • They May Cancel All or Part of Each Other • They Are Cumulative

  6. Units • Forces are measured in units known as • Newtons =N

  7. Forces and Motion • Example Problem • Two horizontal forces of 225N and 165N are exerted in the same direction on a crate. What is the net force on the crate?

  8. Forces and Motion • Solution 225N 165N

  9. Forces and Motion • Solution 390N

  10. Forces and Motion • Example Problem • If the same two horizontal forces of 225N and 165N are exerted in opposite directions on the crate. What is the net force on the crate?

  11. Forces and Motion • Solution 225N 165N

  12. Forces and Motion • Solution 60N

  13. Forces and Motion • Types of Forces • Friction (Ff or f ) • Opposes Horizontal Motion • Parallel to Surface • Normal (FN) • Exerted by Surface on the Object • Perpendicular to Surface

  14. Forces and Motion • Types of Forces • Tension (FT) • Pull or Push Exerted by Secondary Object • Parallel to Secondary Object • Weight (Fg) • Long Range Force Exerted by Gravity on the Object • Toward the Center of the Earth

  15. Forces and Motion • Free Body Diagrams • Illustrate All Forces Acting on an Object

  16. Forces and Motion • Combining Forces

  17. Forces and Motion • Friction Types • Static Friction (fs) (Before motion) • Kinetic friction (fk)(After motion) • Rolling Friction • Reduced Area of Contact • Fluid Friction • Drag (fdrag)

  18. Forces and Motion • Earth’s Gravity • Force Pulling all Objects Toward the Center of the Earth • g is the acceleration of Gravity (-9.8 m/s2) • Galileo Galilei (1564-1642)

  19. Newton’s Laws of Motion 1

  20. Forces and Motion • Newton’s First Law of Motion • “Every Body Continues In Its State of Rest, Or of Uniform Motion In A Straight Line, Unless It is Compelled to Change That State by Forces Impressed Upon It.”

  21. Forces and Motion • Newton’s First Law of Motion • “Every Body Continues In Its State of Rest, Or of Uniform Motion In A Straight Line, Unless It is Compelled to Change That State by Forces Impressed Upon It.” • aka “The Law of Inertia”

  22. Forces and Motion • Inertia • The Tendency of an Object to Resist a Change in Movement • Equilibrium • Net Force = 0

  23. Newton’s Laws of Motion 2

  24. Forces and Motion • Newton’s Second Law of Motion • “The Acceleration of a Body is Directly Proportional to the Net Force Acting on the Body and Inversely Proportional to the Mass of the Body.”

  25. Forces and Motion • Newton’s Second Law of Motion • The Greater the Force on the Object, the Greater the Acceleration of the Object • The Greater the Mass of the Object, the Weaker the Acceleration of the Object

  26. Forces and Motion • Newton’s Second Law of Motion • Force is Related to… • The Mass of the Object (m) • The Acceleration of the Object (a)

  27. Forces and Motion • Measurement of Force • SI Units • Mass - Kilogram (kg) • Distance - Meter (m) • Time - Second (s)

  28. Forces and Motion • Measurement of Force • The Newton (N) • One Newton can accelerate 1 kg to 1 m/s2 • N = 1 kg*m/s2

  29. Forces and Motion • Weight • The Force of the Acceleration of Gravity on the Mass of an Object

  30. Newton’s Laws of Motion 3

  31. Forces and Motion • Interaction Forces • Newton’s Third Law of Motion • “When anObject Exerts a Force On a Second Object, That Second Object Exerts an Equal and Opposite Force On the First Object.”

  32. Forces and Motion • Interaction Forces • Newton’s Third Law of Motion • “For Every Action There is an Equal and Opposite Reaction”

  33. Forces and Motion • Momentum • Product of an Object’s Mass and Its Velocity • Large Mass/ Low Velocity = Small Mass/ High Velocity

  34. Inelastic collisions • M1V1=M2V2 • Example • A 4.5-kg ham is thrown into a stationary 15-kg shopping cart. At what speed will the cart travel if the ham had an initial speed of 2.2 m/s?

  35. Forces and Motion • Universal Forces • Electromagnetic • Attract and Repel • Electric • Opposites Attract (Charged Particles) • Magnetism • Opposites Attract (Polarized Metal Molecules) • Nuclear • Strong and Weak in Nucleus of Atom • Gravity

  36. Forces and Motion • Gravity • Every Object in the Universe Attracts Every Other Object • Force Relative to the Inverse of the Distance • Proportional to Mass • Acts over Great Distances

  37. Forces and Motion • Orbits • Orbits are Maintained by the Velocity of the Object Perpendicular to Gravity • Centripetal Force

  38. Forces and Motion • Homework

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