PASCO Xplorer-GLX Users’ Guide - Manual (Page 121)

X p l o r e r G L X U s e r s ’ G u i d e 115
A c t i v i ty 4 : N e w to n ’s L a w o f C o o l i n g
Background
Newton’s Law of Cooling states that the rate of temperature change of a body is
proportional to its relative temperature, r, or the body’s temperature minus the
temperature of the surroundings. Mathematically, Newton’s Law of Cooling can
be written:
(eq. 1)
where dT/dt is the rate of temperature change and k is a constant greater than 0.
Another way to write Newton’s Law of Cooling is
(eq. 2)
where r is the relative temperature at time t, and r
0
is the relative temperature at
t = 0. A graph of Equation 2 is shown to the right.
In this experiment, you will record and graph the temperature of a hot object (a
test tube full of sand) as it cools. You will then compare the experimental data
with the theoretical graph.
Before You Begin
Start a new experiment on the GLX.
1. Press to go to the Home Screen.
2. Use the arrow keys to highlight the Data Files icon and press to open
the Data Files screen.
3. Press to open the Files menu and press to select New File.
4. When the GLX asks if you would like to save the previous file, press
to save or not to save.
Equipment Quantity
Xplorer GLX 1
Fast-response Temperature
Probes
2
Styrofoam Cups 2
Test Tube 1
Tape 10 cm
Sand 100 g
Hot Water (50 to 70 °C) 500 mL
dt
dT
------ kr – =
time
relative temperature
r
0 r r
0
e
k t –
=
F4 1 pqrs
F1
F2