Physics Flashcards
what is kinetic energy? how is it calculated? and what is the SI unit?
K= 1/2mv^2
SI unit is J or Joules
what is Joule (J) equal to?
kg x m^2 divided by seconds squared
Kinetic energy is a function of the _______ of speed. If speed doubles, the kinetic energy will ________, assuming the mass is constant.
square
quadrupled
How is gravitational potential energy calculated?
U=mgh
U is potential energy, m is the mass in kg and h is the height
tripling the height or tripling the mass of the object, will do what to the gravitational potential energy?
increase it by a factor of 3
what is elastic potential energy? what is it determined or calculated with?
when springs are stretched or compressed from its equilibrium length, the spring has elastic PE
U= 1/2kx^2
k is the spring constant, x is the measure of displacement from equilibrium
how is total mechanical energy calculated?
E=U+K
U is potential energy and K is kinetic energy
what does the first law of thermodynamics account for?
energy can neither be created nor destroyed- it can only be transfered from onw form to another
what are conservative forces?
path dependent and do not dissipate energy
most commonly they have potential energy associated with them ex: gravtiational and electrostatic forces
what are examples or conservative forces? non conservative forces?
conservative forces: gravity and electrostatic forces. they conserve mechanical energy
nonconservative forces: friction and air restistance. they dissipate mechanical energy as thermal or chemical energy
what is work?
the process by which energy is transferred from one system to another
what forces are capable of doing work?
only forces parallel or antiparallel to the displacement vecotr will do work (that is transfer energy)
work and energy are not the same thing. work is the process by which a quantity of energy is moved from one system to another
when do we say that work was done by the gas and the work is positive?
when a gas expands
when do we say that work was done on the gas and the work is negative?
when a gas is compressed
how do you calculate the work done on or by a system?
by finding the area under the pressure-volume curve
If the volume stays constant as pressure changes then how much work is done?
no work is done because there is no area to calculate
what is the work done on a system in an isovolumetric or isochoric process?
no work is done because the volume is constant as pressure changes
If pressure remains constant as volume changes ( isobaric processes), then how is the area under the curve calculated?
the length of P and the width change in V so with isobaric processes where pressure is constant work is calculated as
W=P x change in V
what is Power? and what are the SI units for it?
a measure of the rate of energy consumption, transfer or transformation per unit time
P= W/t= change in E/t
SI unit is watt (W), which is equal to J/s
power can also be calculated in circuits, resistors and capacitors and it is known as electric power. what is the equation for electric power?
P= IV
I is current and V is electrical potential difference (voltage)
what is the relationship between work and energy?
there is a direct relationship between the work done by all the forces acting on an object and the change in kinetic energy of an object
when one calculates the change in kinetic energy, experieinced by an object, then what is the net work done on or by an object?
the same as the change in kinetic energy
how is the first law of thermodynamics expressed?
the change in systems internal energy (U) is equal to the heat transferred into the system (Q) minus the mechanical work done by the system (W)
change in U= Q - W
when is Q ( heat transferred into the system) positive? and when is it negative?
positive when heat flows into the system
negative when heat flows out of the system