IS 4th

• What are the conditions for work to be done?


  There must be force, displacement, and the displacement must be parallel to the force
• Is there force being done? A waiter carrying a loaded tray in his steady arm across a room at a constant speed

  No, because the force is acting upwards on the tray and the displacement is not parallel
• What is a Joule

  Measurement for work and energy, Newton Meters (Nm)
• Can work be positive, negative, or 0?


  Yes: its + when force is in the same direction as the displacement, its - when force is in the opposite direction as the displacement and the frictional force is opposite, and it is 0 when force is perpendicular to the displacement
• Why is work scalar?


  Work is scalar because it only has magnitude and no direction, and is a dot product of two vectors
• What is the equation for work?


  W = Fd
• What is the equation for work when there is an angle?


  W = Fd cos
• 1 Horsepower = 


  746 Watts
• What is power?


  The rate of doing work (Fd)
• The equation for power is


  P = W/t
• What is the relationship between P and t?

  Inversely proportional: one goes up, other goes down
• What is a watt?

  Measurement for power, J/s : joules per second
• What kind of quantity is power

  Scalar
• What is energy


  Its the ability and physical quantity that allows us to do work
• 2 forms of mechanical energy


  KE, PE: GPE & EPE
• Formula for KE:


  $mv^2/2$
• Formula for GPE:


  mgh
• Formula for EPE:


  $kx^2/2$k = spring constant (N/m) & x = displacement
• What is the work-energy theorem


  It states that when work is done, energy is transferred
• What is the relationship of KE and speed


  When speed is doubled, KE quadruples. Since the equation (mv^2/2) implies it takes four times the work to double the speed.
• Relationship of GPE to h and m

  GPE increases as height and mass increase
• What is the formula for the work-energy theorem

  $mv^2f/2 - mv^2i/2$
• Law of Conservation of Mechanical Energy

  Energy can neither be created or destroyed, but can only be converted
• Formula for the total energy of an object

  ME = KE + PE
• Dissipative forces

  non-conservative forces that do work, such as kinetic friction and air drag
• Formula for Conservation of ME

  MEi = MEf or KEi + PEi = KEf + PEf