Speed, Velocity, and Acceleration

• Object positions, force directions, and motions are compared using a chosen reference frame and chosen units of size.
• Speed is the change in position of an object per unit of time.
  • Speed always has a positive value and is non-directional.
• Velocity is the speed an object moves.
  • Velocity may have a positive or a negative value depending on the direction of the change in position.

• Acceleration is the change in velocity per unit of time.
  • An object moving with constant velocity has no acceleration.
  • A decrease or increase in velocity are considered acceleration.
  • A distance-time graph for an accelerating object is always a curve.
  • Objects moving with circular motion are constantly accelerating because direction (and hence velocity) is constantly changing.
• Formulas (mathematical models) are used to calculate speed, velocity, and acceleration.
• Graphs (2-D models) are constructed to better understand relationships and patterns of motion.

• apply the concepts of speed, velocity, and acceleration and related models and graphs

Mass and Weight

• Mass and weight are not equivalent.
  • Mass is the amount of matter in a given substance.
  • Weight is a measure of the force due to gravity acting on a mass.
  • Weight is measured in Newtons and mass in kilograms .

• understand how mass and weight differ

Newton's Laws

• Forces cause motion.
• Forces can cause objects to move, stop moving, change speed, or change direction.
• Newton's laws describe the motion of all common objects.
• Force is measured in Newtons.
• The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change.
• The greater the mass of the object, the greater the force needed to achieve the same change in motion.
• For any given object, a larger force causes a larger change in motion .
• A variety of models can be used to illustrate Newton's laws of motion.


• NEWTON'S FIRST LAW  states that an object at rest will remain at rest and an object in motion will remain in constant straight motion unless acted on by an external force .

• NEWTON'S SECOND LAW states that force equals mass times acceleration.
  • Net force and acceleration are directly proportional.
    • As the net force increases, the acceleration increases by the same proportion.
  • Acceleration and mass are inversely proportional.



• NEWTON'S THIRD LAW states that for every force there is an equal and opposite force.
• Forces always occur in pairs.
  • For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction.
• Work is done when an object is moved through a distance in the direction of the applied force.
• Friction impedes motion when two surfaces are in contact.

You should understand

• Newton's Laws of Motion
  • how second law shows relationsip among force, mass and acceleration - f = m x a
  • how third law relates to colliding objects
• direction of force of friction
  • that force must be applied continually to keep an object moving due to friction

Simple Machines

• Power is the rate at which work is done.
• A simple machine is a device that makes work easier.
• Simple machines have different purposes:
  • to change the effort needed,
  • to change the direction or distance through which the force is applied,
  • to change the speed at which the resistance moves, or
  • a combination of these.
• Due to friction, the work put into a machine is always greater than the work output.
You should understand
• concepts of work and power
• how simple machines make work easier
• how friction affects work