Science 8 - Physics, Astronomy, Chemistry, Biology

• Force


  A push or pull acting on an object
• Examples of forces


  • Gravity
  • Friction
  • Magnetism
  • Applied forces
• Forces


  • Cause an object to change its speed, direction, or both
• Applied force


  Force that a person or thing applies to another object
• Balanced forces


  Forces acting on an object from opposite directions that are equal
• Unbalanced forces


  Forces acting on an object from opposite directions that are not equal
• Balanced forces


  Objects with balanced forces acting upon them will most likely be still - not moving
• Unbalanced forces


  Objects with unbalanced forces acting upon them are in motion - moving
• Tug-of-war examples

  • Top image: Balanced forces (draw)
  • Bottom image: Unbalanced forces (left side winning)
• Inertia


  The "stubbornness" of an object to a) stay at rest, b) stay in motion, or c) stay moving in one direction
• Nothing moves from sitting, stops from moving, or changes direction without an outside force acting on it (Newton's 1st Law of Motion; "Law of Inertia")
• Gravity


  The force that pulls everything toward the center of the earth
• In the Catapult Lab, objects of small mass were less affected by gravity and flew faster and further than objects with greater mass
• Greater mass of an object


  Slower speed and shorter distance the object flies due to gravity and air resistance
• Friction


  A force that works against motion; the action of one surface or object rubbing against another surface or object
• Air resistance


  A type of friction that slows things down that are moving through the air
• Momentum


  The amount of mass an object has multiplied by its velocity
• The larger the mass of an object in motion, the more momentum it will have than objects with smaller mass, if the velocities are similar
• The more velocity an object has in motion, the more momentum it will have than objects with less velocity, if the masses are similar
• A baseball and a large truck both traveling at 55 mph

  The truck with much more mass will have much more momentum and it will take much more energy to stop the truck than the baseball
• Speed


  Calculated as distance divided by time
• Calculating distance

  Time x Speed = Distance
• Calculating distance examples

  • 1 hour at 30 mph = 30 miles
  • 2 hours at 30 mph = 60 miles
  • 3 hours at 40 mph = 120 miles
• The appearance or shape of the graph does not represent the shape of the path or ground
• Graph line segments


  • Higher coordinate = further away from home
  • Steeper line segment = faster speed
  • Straight line segment = traveler has completely stopped