Chapter 6 - Work and Energy Flashcards
What type of quantity is work?
Scalar Quantity
Formula for Work
W(work)=F(force)•s(displacement)
Unit of work
Joule(J) = N(Newton)•s(meter)
Work done when force is applied but displacement is zero?
Absolutely none
Work done at an angle
W=(Fcosθ)s
Result of work
Change in kinetic energy of an object
Relationship that relates work in kinetic energy
Work-energy theorem
Work-energy theorem expression
(ΣF)s=1/2mvᶠ²-1/2mvᴼ²
Equation for the kinetic energy of an object
KE=1/2mv²
Why does a moving object have Kinetic Energy?
A moving object has kinetic energy because work was done to accelerate the object from rest to a speed vᶠ
When does the work-energy theorem not work?
The work-energy theorem deals with the work done by the net external force. The work-energy theorem does not apply to the work done by an individual force, unless that force happens to be the only one present, in which case it is the net force.
Formula pertaining to work done by gravity/potential energy
W(gravity)=mg(ho-hf)
Energy possessed by an object in motion
Kinetic Energy
Energy an object possessed by virtue of its position relative to the earth
Gravitational Potential Energy
The greater the height, the greater is the potential to do work, meaning?
The greater is the Gravitational Potential Energy
Formula for Gravitational potential energy
PE=mgh
A force is __ when work it does on a moving object is independent of the path between the object’s initial and final positions; A force is __ when it does no net work on an object moving around a closed path, starting and finishing at the same point
Conservative force
Potential energy in a closed path
0J
A force is _ if the work it does on an object moving between two points depends on the path of motion between two points, such as kinetic frictional force.
Nonconservative force
Formula for net work done by nonconservative force
Wnc = (KEf - KE0 ) + (PEf - PE0 ) or Wnc = ΔKE + ΔPE
Sum of Kinetic energy and gravitational potential energy
Total Mechanical Energy
Equation for Total Mechanical Energy
Wnc = (KEf + PEf) - (KE0 + PE0) or Wnc = Ef - E0
Principle of Conservation of Mechanical Energy states that
Total mechanical energy is conserved when Wnc=0
A term that incorporates both work and time
Power
Equation for Power
P= Work/ Time
Unit for Power
Joule / Second = Watt
The rate at which the energy is changing
Power
Energy can neither be created or destroyed, but can only be converted from on form to another.
The principle of conservation of energy
