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forces. DEFINITION OF FORCE. Types Units. Definition of a Force. Forces are any push or pull on an object Created by contact or at a distance Forces are portrayed by arrows on pictures, with the arrow pointing in the direction of the force

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  1. forces


  3. Definition of a Force Forces are any push or pull on an object Created by contact or at a distance Forces are portrayed by arrows on pictures, with the arrow pointing in the direction of the force The size of the arrow indicates the size of the force

  4. How do you know if you are applying a force?

  5. How forces effect objects • Balanced: when all forces applied to an object cancel each other out. • Results in NO change in motion • (Constant velocity)

  6. Unbalanced forces • Definition: Where more force is pushing or pulling on object in one direction than opposite direction • Results in a change in motion (Acceleration)


  8. Forces Contact (applied) Forces Electromagnetic forces (most common) Non-contact Forces Gravitational (most common) Fields

  9. Types of forces Contact forces: source of force is a push or pull that results from direct contact between the surfaces of 2 or more objects. Related to the forces that repel or attract molecules and/or atoms Field forces: source of force applies influence over a distance, not direct contact

  10. Examples ContactField Applied Gravitational Friction Electric Ground Magnetic Air Resistance


  12. Gravity Force of attraction between 2 objects that have mass Fg or W

  13. What determines the gravitational pull? The mass of each object The distance between the items

  14. Gravitational force Depends on: The amount of mass in each object The larger the masses, larger the force The amount of distance between each object The greater the distance, the smaller the force The effect on force of gravity by distance is exponential, mass is linear

  15. Law Universal Gravitation There is a gravitational attraction between any two items that have mass. The amount of the force is related to the mass of each object and the distance their centers are apart More mass, less distance  greater force

  16. Do you think Weight of an object is… An applied force A gravitational force A magnetic force

  17. Weight = force on object due to gravity • If there is no big object near you, you have no weight


  19. Blackholes

  20. Black hole stripping matter from nearby star

  21. Black holes are Some the strongest sources of gravitational pull in the universe The remains of dying stars Stars much larger than ours (20x) Objects that collapse in on itself because of gravity, become impossibly dense, compact

  22. Weight influences shape Tree trunks Jelly fish Humans 10 feet tall

  23. Biological connection Blood pressure is related to gravity More in lower part of body than upper Take blood pressure on arm because same position as heart

  24. Blood pressure and gravity


  26. Applied/Contact force On a macroscopic level Any force that results from contact between two objects or the environment Electromagnetic in nature, the repulsion between atoms Some applied forces are further identified (normal force)

  27. Examples Ex. The forces of a hand pushing a box The force of the rope pulling on a horse’s bridle Others?

  28. What applied force is pushing the rocket upward?

  29. Measuring Mass and weight

  30. What does mass mean?

  31. Mass • As previously defined: • The amount of stuff, or matter that composes an object • More matter = more massive an object • Does not depend on location of object like weight. Mass ≠ Weight

  32. Weight and mass Are related, not the same Mass is not a force, but a measurement of matter. Weight is the gravitational pull of earth Weight changes as the objects moves around the universe, mass will not

  33. Units of mass • For chemistry (grams) • For Physics (kilograms) • 1 kg = 1000 g

  34. Which is more massive? A kilo of feathers or A kilo of marbles

  35. Difference in mass

  36. Inertia • Resistance to change in motion • Measured by mass of object • More mass, more inertia • Inertia is NOT a force, but a measure of resistance


  38. Measurement of Force • In USA, force (weight) is measured in pounds (lbs) • In most of the rest of the world, force (weight) is measured in Newtons (N)

  39. Determining weight in newtons Weight is the measure of the Force of gravity To find your weight in Newtons: Take your weight and divide it by 2.2 (mass) Take the result and multiply it by 9.8 (force)

  40. Calculate your mass value Take your weight in Newtons and divide by 10


  42. Units Some units that are made out of 2 or more fundamental units are renamed after a Famous Scientist Units of Force 1 Kg (m/s2) = 1N (Newton)

  43. WHAT WEIGHS 1000 N?

  44. Football player (220 lbs)

  45. WHAT WEIGHS 100 N?

  46. Freshman backpacks (22 lbs)

  47. WHAT WEIGHS 10 N?

  48. The average textbook (2.2 lbs)

  49. WHAT WEIGHS 1 N?

  50. A smallish apple (0.22 lbs)

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