Physics Flashcards
When is the work done by a force zero
When the force applied is Perpendicular to the displacement at it’s point of action
Work-Kinetic Energy theorem
K=½mv²
Calculations of work done when there is a change in kinetic energy
1. For distance
W = ∫ ΣF dx = ∫ Σ ma dx
2. For velocity
W =∫ Σ mv dx]
Gravitional potential energy
is the energy associated with an
object at a given location above the surface of the Earth.
How do you determine the work done when given the gravitational potential energy
Types of energy review
a.Kinetic Energy:
Associated with movement of members of a system
b.Potential Energy:
Determined by the configuration of the system such as Gravitational and Elastic Potential Energies
c. Internal Energy:
Related to the temperature of the system
Types of systems
a. Non-isolated systems:
-Energy can cross the system boundary in a variety of ways.
-Total energy of the system changes
b.Isolated systems:
- An isolated system is a system that has no net external force acting on it.
-Energy does not cross the boundary of the system
-Total energy of the system is constant
c.Conservation of energy
-Can be used if no non conservative forces act within the isolated system
-Applies to biological organisms, technological systems, engineering situations, etc
Ways to transfer energy
Work
transfers energy by applying a force and causing a displacement of the point of application of the force.
Mechanical Wave
transfers energy by allowing a disturbance to propagate through a medium.
Heat
the mechanism of energy transfer that is driven by a temperature difference between two regions in space.
Matter Transfer
matter physically crosses the boundary of the system, carrying energy with it.
Electrical Transmission
energy transfer into or out of a system by electric
current.
Electromagnetic Radiation
energy is transferred by electromagnetic waves.
Energy conservation
Energy cannot be created nor destroyed but can be transfered
Examples of nonconservative forces (net external force) are;
a. Friction
b. Air resistance/drag
c. Push-pull forces.
Consider a ball in free fall, Which systems is this ball and determine the speed of the ball at a height y above the ground (In your working use energy insteand of motion)
What is Finalize the equation for V is consistent with the results obtained from the particle under constant acceleration model for a falling object.
Define power and write the eqn
Power is the time rate of energy transfer.
Interms of work
P= w/t
Interms of energy
P= dE/dt
Write conservation of energy in the body eqn and first law of thermodynamic eqn
a.Conservation of energy in the body eqn
(Change in stored energy) = Heat lost from the body + Work done
b.Thermodynamic eqn
∆U= ∆Q + ∆W
Where;
∆U is the change in stored energy
∆Q is the heat lost or gain
∆W is the work done by th body
Note; At a constant temperature to lose heat to its surroundings , and ∆ Q is negative. ∆U is also negative, indicating a decrease in stored energy.
