Physics Unit

• What are the names of the two kinds of motion that Aristotle classified?

  Natural motion and violent motion
• Natural motion

  Motion that is straight up or straight down (light things rise, heavy things fall)
• Violent motion

  Imposed motion resulting from an external push or pull (unnatural motion)
• Who believed that heavy objects fall faster than light objects?

  Aristotle
• Who believed that moving objects must have force exerted on them to keep them moving?

  Aristotle
• Galileo showed that dropped objects fall to the ground at the same time - air resistance is negligible
• Galileo discovered that in the absence of friction, no force is necessary to keep a horizontally moving object moving
• In an experiment, Galileo concluded that balls rolling down inclined planes and then up others tend to roll back up to their original heights
• The tendency of a moving body to keep moving is natural - every material object resists change in its state of motion
• The property of things to resist change is called inertia
• The use of inclined planes for Galileo's experiments helped him to discover the property called inertia
• A ball rolling along a level surface slowly comes to a stop. How would Aristotle and Galileo explain this?

  Aristotle: no force applied

  Galileo: opposing force
• greater mass = greater inertia
• smaller mass = smaller inertia
• The amount of inertia possessed by an object depends on the amount of matter (its mass)
• Mass


  The quantity of matter in an object
• Mass


  Measure of inertia or sluggishness that an object exhibits in response to any effort made to start it, stop it, or change its state of motion in any way
• Weight

  Amount of gravitational pull on an object
• Weight is proportional to mass
• Twice the mass = twice the weight
• half the mass = half the weight
• Mass involves how much matter an object contains
• Volume involves how much space an object occupies
• The concept of inertia mostly involves mass
• The standard unit of measurement for mass is known as a kilogram
• On Earth's surface, 1 kilogram weighs 10 newtons
• Away from Earth, 1 kg of material weighs less than 10 newtons
• When the string is pulled down slowly, the top string breaks which best shows the weight of the ball

  
• When the string is pulled down quickly, the bottom string breaks with best illustrates the mass of the ball

  
• Density is the measure of how much mass occupies a given space
• Density = mass/volume
• The density of 1 kilogram of iron is the same on the Moon
• Force


  Simply a push or pull
• Force is a vector quantity because it has both magnitude (how much) and direction
• Net force

  Combination of all forces
• Net force changes an object's motion
• A cart is pushed to the right with a force of 15 N while being pulled to the left with a force of 20 N. The net force on the cart is?

  5 N to the left
• The equilibrium rule

  The vector sum of forces acting on a non-accelerating object or system of objects equals zero
• The equilibrium rule applies to vector quantities
• Support force is force that supports an object on the surface against gravity