Describe how conservation of energy relates to the first law of thermodynamics.
Identify instances of the first law of thermodynamics working in everyday situations, including biological metabolism.
Calculate changes in the internal energy of a system, after accounting for heat transfer and work done.
The information presented in this section supports the following AP® learning objectives and science practices:
4.C.3.1 The student is able to make predictions about the direction of energy transfer due to temperature differences based on interactions at the microscopic level.
(S.P. 6.1)
5.B.4.1 The student is able to describe and make predictions about the internal energy of systems.
(S.P. 6.4, 7.2)
5.B.7.1 The student is able to predict qualitative changes in the internal energy of a thermodynamic system involving transfer of energy due to heat or work done and justify those predictions in terms of conservation of energy principles.
(S.P. 6.4, 7.2)
If we are interested in how heat transfer is converted into doing work, then the conservation of energy principle is important. The first law of thermodynamics applies the conservation of energy principle to systems where heat transfer and doing work are the methods of transferring energy into and out of the system. The
first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer
into the system minus the net work done
by the system. In equation form, the first law of thermodynamics is
Here
is the
change in internal energy
of the system.
is the
net heat transferred into the system —that is,
is the sum of all heat transfer into and out of the system.
is the
net work done by the system —that is,
is the sum of all work done on or by the system. We use the following sign conventions: if
is positive, then there is a net heat transfer into the system; if
is positive, then there is net work done by the system. So positive
adds energy to the system and positive
takes energy from the system. Thus
. Note also that if more heat transfer into the system occurs than work done, the difference is stored as internal energy. Heat engines are a good example of this—heat transfer into them takes place so that they can do work. (See
[link] .) We will now examine
,
, and
further.
the transfer of energy by a force that causes an object to be displaced; the product of the component of the force in the direction of the displacement and the magnitude of the displacement
A wave is described by the function D(x,t)=(1.6cm) sin[(1.2cm^-1(x+6.8cm/st] what are:a.Amplitude b. wavelength c. wave number d. frequency e. period f. velocity of speed.
A body is projected upward at an angle 45° 18minutes with the horizontal with an initial speed of 40km per second. In hoe many seconds will the body reach the ground then how far from the point of projection will it strike. At what angle will the horizontal will strike
Suppose hydrogen and oxygen are diffusing through air. A small amount of each is released simultaneously. How much time passes before the hydrogen is 1.00 s ahead of the oxygen? Such differences in arrival times are used as an analytical tool in gas chromatography.
the science concerned with describing the interactions of energy, matter, space, and time; it is especially interested in what fundamental mechanisms underlie every phenomenon