The Nature of Force and Motion

1
The Nature of Force and Motion

1. Force A push or a pull How strong it is and
   in what direction?
2. Net Force The sum of all forces acting on an
   object.
3. Unbalanced Forces can cause an object to start
   moving, stop moving, or change direction. An
   Unbalanced Force will cause an object to
   Accelerate (A Net Force gt 0).
4. Equal forces Forces equal in strength, acting
   in opposite directions. Balanced Forces acting on
   an object will NOT change the objects motion
   (Net Force 0).

2
The Nature of Force and Motion

• Inertia The tendency of an object to resist
  change in its motion.
• Mass The amount of matter in a n object. The SI
  or metric units used for mass will be the
  kilogram (kg) or gram (g).
• Newtons 1st law of Motion An object at rest
  will remain at rest and an object that is moving
  at constant velocity will continue moving at
  constant velocity unless acted upon by an
  unbalanced force.
• Velocity Speed in a given direction.
• Distance / Time in a given direction

3
The Nature of Force and Motion

• Acceleration The rate at which velocity changes
  over time.
• Acceleration due to gravity 9.8m / s 2
• 10. Speed Distance covered per unit time
  Distance / Time
• Momentum Depends on the mass and velocity of an
  object
• Momentum (Kg.m/s) Mass (kg) x Velocity (m/s)

4
The Nature of Force and Motion

• Newtons 2nd Law of Motion The net force of an
  object is equal to the product of its mass and
  its acceleration.
• Force N Mass kg x Acceleration
  m/s2
• F ma
• 13. Newton 1 Newton N 1kg x 1 m/s2
• One Newton is the force required to accelerate a
  1 kg mass 1 m/s2.

5
The Nature of Force and Motion

1. Friction The force that one surface exerts on
   another when the two surfaces move against each
   other. Ex. Air Resistance
2. The Nature of Friction Friction opposes motion.
   Eventually friction will cause an object to come
   to a stop.
3. The Strength of Friction Depends on two things,
   the types of surfaces involved and how hard the
   surfaces come into contact with each other.
   Friction can be both useful and harmful.

6
The Nature of Force and Motion

• Sliding Friction Two solid surfaces sliding
  over each other. Ex. sled over snow
• 18. Rolling Friction When an object rolls over
  a surface. Ex. Bowling ball rolls down the lane
• 19. Fluid Friction The friction that occurs
  when an object moves through a fluid. Ex. The oil
  in a car engine

7
The Nature of Force and Motion

• 20. Gravity The force that pulls objects toward
  the Earth.
• Gravity 9.8 m/s/s 9.8 m/s2
• 21. Free Fall When the only force acting on an
  object is gravity the object is said to be in
  free fall. Fall for 10 seconds Velocity of
  98m/s

8
The Nature of Force and Motion

• 22. Projectile Motion A ball that is thrown
  horizontally from a certain height hits the
  ground at the same time as a ball dropped from
  the same height.

9
The Nature of Force and Motion

• Air Resistance Terminal Velocity When the
  fluid friction from the air resistance equals the
  force of gravity acting on the object, the object
  has reached terminal velocity. This is the
  greatest velocity the object can obtain.
• Weight The measure of the force of gravity
  acting on the mass of an object.
• Weight (N) Mass (kg) x (9.8 m/s2)
• 25. Universal Gravitation The force of gravity
  acts between all objects in the universe.

10
The Nature of Force and Motion

• Newtons 3rd Law of Motion If one object exerts
  a force on another object, then the 2nd object
  exerts a force of equal strength in the opposite
  direction on the 1st object.
• Newtons 3rd Law of Motion - For every action
  force there is an equal in strength and opposite
  in direction reaction force. Ex. A ball hits the
  wall and bounces back.
• Momentum The momentum of an object is equal to
  the product of the objects mass and its
  velocity.
• Momentum kg.m/s mass kg x velocity m/s

11
The Nature of Force and Motion

• 29. Rockets The rocket can rise into the air
  because the gases they expel with a downward
  force exert an equal but opposite force on the
  rocket.
• Satellites An object that travels around
  another object in space. Always Accelerating!
  
• Centripetal Force Any force that causes an
  object to move in a circle.

12
The Nature of Force and Motion

• 32. The Law of Conservation of Momentum The
  total momentum of any group of objects remains
  the same unless outside forces act on the
  objects.