Physics

• Newton’s third law:

  • Forces are not equal and opposite
  • They do not always coexist
  • Normal force does not always push up
  • They do not act on separate objects
• Calculating newtons and gravity forces: 10 n/kg
• When you jump, normal force isn’t present
• In an elevator:

  • There is still normal force
  • When the elevator moves, it might make you think you weigh more
• When you walk up a hill:

  • You accelerate upward
  • Normal force is tricked, so it may think you weigh more
  • Normal force gets bigger
• Inertia:

  • Object’s resistance to change in motion
  • When something is moving, it stays moving
  • When it is at rest, it stays at rest
• Constant Velocity:

  • You stay at the same speed in the same direction
  • There is no acceleration
• Net force:

  • Anything at rest or constant velocity has a net force of 0 (no acceleration)
• Acceleration (vector):

  • How fast you go in what direction
  • Change in speed over time
  • Slower, faster, or turning is acceleration
• F=MA:

  • Calculating net forces
  • A = Acceleration or m/s^2
  • M = Kg
  • F = Newtons
  • Acceleration is a ratio of F:M or force/mass
• Free fall (vacuum):

  • No air resistance
  • Vacuum equation = 10 m/s^2 x kg = newtons
• Terminal Velocity:

  • The velocity of a falling object continuing down after its weight has been balanced off by air resistance
  • Stops acceleration
• Two objects of the same size, but unequal weights are dropped from a tall tower. Which falls first? The heavier object
• Action/reaction pair:

  • There are no isolated forces, always occurring in pairs
  • Example: wall force could not exist without something leaning on it
• Equal and opposite reactions:

  • Every action reaction needs equal and opposite force
• Friction:

  • Opposes motion
• Going up:

  • Acceleration decreases
• Going Down:

  • Acceleration increases
• Air resistance:

  • Causes things to fall at different rates
  • Pushes upward on different sizes of the object causing it to slow down
  • Lighter objects have stronger air resistance
  • Heavier objects have weaker air resistance
• Things in rest and motion are at constant velocity
• If you throw a ball or coin in the air:

  • The only force acting on it is gravity
• Constant Acceleration:

  • Change in velocity over time
• If you throw a rock in the air:

  • It stops because gravity is constantly acting
  • It is 0 when it stops, but goes by 10 when it moves
• When someone goes down in an airplane:

  • They go down by 10
  • The increase in speed is smaller, but they are still at acceleration until they turn into terminal velocity
• Equal opposite:

  • When gravity pulls you down, you are pulled up with the same force
• More mass is more inertia
• Net force:

  • The sum of all forces and has directions
• Velocity - speed of something in a given direction