Accelerated Physical Science
Mr. Mahlum
Science Swings with
Mass and the Inertial Balance
Introduction
Mass is defined as the amount of
matter in an object. Weight is defined as the force of
gravity on an object. Although they are
often used interchangeably in everyday language, mass and weight are not the
same thing. If an elephant was loaded
into a spaceship and flown into orbit around the Earth, the elephant would be weightless because the force of gravity
is almost non-existant once you have escaped the gravitational pull of the Earth. However, that same elephant would still be
made of a lot of matter. We would still
say that the elephant was massive,
despite the fact that the elephant was weightless.
On Earth we typically measure mass using a
scale. Scales measure mass by observing
the force of gravity acting on objects.
Scales however are not useful in environments such as space, where the
force of gravity is almost non-existant.
To measure the mass of objects in space we must use a different type of
device, called an inertial balance.
Inertia refers to the tendency of
an object that is at rest to stay at rest, and the tendency of an object that
is in motion to stay in motion. Objects
that have more mass also have a greater inertia. The inertial balance measures the mass of a moving object by
observing its tendency to stay in motion. In this experiment, you will use an inertial balance to determine
the mass of an unknown object.
Materials: Inertial Balance Electronic
Balance 2” C-clamps (six)
Timer Object of Unknown
Mass
Figure 1.
Procedure:
Part I – Calibrating the Inertial Balance
1.
Obtain
an inertial balance and 6 C-clamps of similar size from the instructor.
2.
Using
the electronic scale, find the mass of one C-clamp. Record this number in your data table.
3.
Using
one of the clamps, fasten the balance to the lab bench as shown in Figure 1.
4.
Fasten
one of the C-clamps to the pan of the inertial balance and set the balance in
motion, using a small vibration amplitude (about 2 cm).
5.
Allow
yourself to get synchronized with the motion of the balance before starting the
watch. Start the watch on the count of
“zero” and note the time it takes for 20 complete cycles to the nearest 0.01
seconds.
6.
Record
the total time for 20 cycles in the data table.
7.
Add
additional C-clamps to the pan of the balance and repeat this procedure with 2,
3, 4, and 5 C-clamps.
8.
Calculate
the period (T) of the balance for
each of the trials. Period is equal to
the time it takes for one full cycle. T = total time / number of cycles
9.
Calculate
the period squared (T 2 )
of the balance.
10.
Draw
a graph of Period2 vs. Mass.
11.
Calculate
the slope of the best fit line for the graph.
12.
Determine
the mathematical equation of the best fit line for the graph.
Procedure: Part II.
1.
Obtain
an object of unknown mass from the instructor.
2.
Place
the unknown mass in the inertial balance and determine its period using the
same procedure as in Part I.
3.
Using
the mathematical equation of the best fit line from part I of the lab,
calculate the mass of the unknown object.
(This will be your observed value of mass).
4.
Check
the mass of the object using an electronic balance (This will be your accepted
value of mass).
5.
Calculate
the percent experimental error for your measurement of the unknown objects
mass.
Results: Include the following in your lab report
Written Observations: Describe what happened to the balance as you
added more C-clamps.
Data: Reference
attached pages
Graphs: Reference attached pages
Calculations: Reference
the attached pages with calculations for Slope, Mass of the unknown object, and
% experimental error.
Discussion:
Include the following in your lab report
Analyses of graphs: Write
an analysis for the graph. Include
slope calculations for the straight line graph. Identify the meaning of the slope and the y-intercept. Write the mathematical equation of the line.
Summary of Results: Describe how you calculated the mass of the
unknown object. Report observed and
accepted values and % error.
Sources of Error: Identify
sources of error in the experiment and explain how these might be eliminated if
the procedure was modified and the experiment was repeated.
Conclusion: Briefly conclude the report
and address the initial purpose.
Questions:
Answer in complete sentences at
the end of your lab report.
1.
In
5 sentences or less explain the difference between Mass and Weight.
2.
An
astronaut is in orbit about the Earth.
She has a 1.0 kg box of nails that she places on the inertial balance
and starts in motion. What is the
period of the box of nails?
3.
In
the year 2020, a grocer is living in space aboard the international space
station. A customer wishes to purchase
a bunch of grapes. The grocer uses the
inertial balance to measure the grapes.
He adds the grapes to the balance and measures the period of oscillation. If the period is 0.575 seconds, what is the
mass of the grapes?
4.
If
the grocer is selling grapes for $2.49 per kilogram, how much does he charge
the
customer?
Data Table: Name
______________________
Write your equation for your
best fit line below:
Equation: _______________________
Calculate your observed
value for the mass of the unknown object using the Period2 for the
unknown object and substituting into the equation for the best fit line. Solve this equation to find the mass of the
unknown object (show your work).
Observed Mass = _________________
Measure the mass of the the
unknown object on the electronic balance.
This will be your accepted value fro the mass of the object. Record this number here
Accepted
Mass = __________________
Calculate your percent
experimental error (Show your work)
Percent Error = ___________________