Week 5: Balls and Ramps

 Textbook notes: 

  • Force: a push or pull 
  • Newton's First Law
    • Objects at rest remain at rest, while objects in motion stay in motion unless acted on by an unbalanced external force or every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed on it. 
    • Every object and every motion are all acted on by forces at all times
    • A force is a push or a pull on an object resulting from the object's interaction with another object
    • There needs to be another object acting on it in some way 
  • Why do things move? 
    • Need to apply another force to it that is strong enough to make it move
    • In order to move, one side must have a bigger pull or force 
      • The forces must be unbalanced to make something move 
    • Objects remain at rest while objects in motion stay in motion unless acted on by an unbalanced external force 
  • Why do things stop moving? 
    • Friction 
      • A force that holds back the motion of a sliding object or resistance to motion of one object moving relative to another 
    • Kinetic friction 
      • Generated when things are moving 
    • Static friction 
      • Present even when objects are staying still 
  • What affects how objects move? 
    • Inertia 
    • heavier objects require a bigger push or force to move 
    • Heavier objects have more inertia 
    • Objects with greater inertia require more force to change their motion: to start moving, stop moving, or change direction.
  • Newton's Second Law 
    • The greater the mass of an object, the more force it will take to accelerate the object or force is equal to the change in momentum (mV) per change in time. For a constant mass, force = mass x acceleration. 
  • What factors affect force & how objects move? 
    • Mass 
    • Speed 
    • Direction 
  • Newton's Third Law 
    • For every action there is an equal and opposite reaction.
    • Rockets are launched into space using Newton's third law 
      • As the rocket fuel burns, it is pushed down out of the rocket as gas, which produces its opposite force that pushes upwards on the rocket, sending it into space
  • Can you make an object move without touching it? 
    • Yes 
      • Gravity 
      • Magnets
      • Electrostatic forces (static electricity) 
  • Bernoulli's Principle
    • As the speed of a moving gas or liquid increases, pressure decreases and vice versa: as the speed decreases, pressure increases. 
    • Airplane wings are curved to take advantage of this 
      • As air flows over the top curved part of the wing, it has to travel at a faster speed because it needs to travel a longer distance than the air going under the wing 
        • This creates a difference in pressure between the top of the wing and the bottom 
        • The top of the wing has low pressure and the bottom has high pressure 
        • The higher pressure generates lift and the airplane flies 

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