Hy Density: Equalizing Matters (Equal Arm Balance)
Teacher Information Page Activity 3B Part 3
Activity Introduction:
Students will make an equal arm balance and describe the difference between
mass and weight. Students will also learn more about how Archimedes would
have set-up his famous experiment to compare the golden crown to the known mass of gold.
The activity takes only five minutes and students will use their equal arm balances in the next
part of the activity.
Activity Background:
Simply dropping a lump of gold in a container of water to determine the volume would not
have given Archimedes an accurate answer to his problem. How would he have gotten the
lump out without spilling more water? What would he compare the displacement to? He
needed more information.
Archimedes was the man who said
“ΠΑ ΒΩ ΚΑΙ ΧΑΡΙΣΤΙΩΝΙ ΤΑΝ ΓΑΝ
ΚΙΝΗΣΩ ΠΑΣΑΝ.”
Sorry, you might not know the ancient
Doric language, of Syracuse.
It is believed that Archimedes combined what he learned in the bathtub
(displacement of water and its relationship to density) and his knowledge of
levers. Before students can do the next
activity they need to make an equal
arm balance, which is a simple balance
made such that the distances from the
Figure 1 – Equal Arm Balance
point of support of the beam to each
pan at the end of the beam are equal,
See Figure 1 Equal Arm Balance. Simple balances were used as early as 5000 B.C. More
modern balances were devised in the 18th century, by the Scottish chemist Joseph Black.
He used a lightweight, rigid beam supported on a thin-edged fulcrum. The accuracy
achieved by this device was impressive.
These instruments operate in a way similar to that of a seesaw. A sample is placed
on one end of the balance and then adding known weight to the other end until
the beam balances.
2007 PROTOTYPE
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3B PART 3
Corpulosity
Translation: “Give me a place to stand
and with a lever I will move the whole
world.” Archimedes is attributed by
many as the person to come up with
the law of the lever.
1
Mass is the amount of material of which an object is made and is measured by using a
balance. The balance allows us to compare an unknown amount of matter to a
known amount of matter. When the beam is completely horizontal, the mass
of the objects on both sides is equal. Thus we can determine the mass of an
object. Weight is the pull of gravity on the mass of an object and is measured
on a scale.
Activity Materials per group:
N
3 large paperclips
N
1 ruler with binder holes
N Weight set or objects such as washers of known mass
N 1 copy of Student Data Page (per student)
N
1 copy of Student Information Page (from class set)
Students will make an equal arm balance similar to that shown in Figure 1 Equal Arm Balance.
Activity Management Suggestions:
Modifications:
Time management may be the issue. This activity is designed to be completed in about 5
minutes, so be sure students understand all directions before starting to assemble the
balances.
Extensions:
2007 PROTOTYPE
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3B PART 3
Corpulosity
Students can research the type of balance(s) used by Archimedes.Use a commercial doublepan balance to determine the accuracy of their balance.
2
Hy Density: Equalizing Matters (Equal Arm Balance)
Student Information Page Activity 3B Part 3
Activity Introduction:
It is believed that Archimedes would have used an equal arm balance to
determine if there was a difference between crown and lump of gold. In this
activity you will make an equal arm balance to use in your next experiment.
Activity Background:
Simply dropping a lump of gold in a container of water to determine the volume would not
have given Archimedes an accurate answer to his problem. How would he have gotten the
lump out without spilling more water? What would he compare the displacement to? He
needed more information.
Archimedes was the man who said
“ΠΑ ΒΩ ΚΑΙ ΧΑΡΙΣΤΙΩΝΙ ΤΑΝ ΓΑΝ
ΚΙΝΗΣΩ ΠΑΣΑΝ.”
Sorry, you might not know the ancient
Doric language, of Syracuse.
It is believed that Archimedes combined what he learned in the bathtub
(displacement of water and its relationship to density) and his knowledge of
levers. Before students can do the next
Figure 1 – Equal Arm Balance
activity they need to make an equal
arm balance, which is a simple balance
made such that the distances from the point of support of the beam to each pan at the end
of the beam are equal, See Figure 1 Equal Arm Balance. Simple balances were used as early as
5000 B.C. More modern balances were devised in the 18th century, by the Scottish chemist
Joseph Black. He used a lightweight, rigid beam supported on a thin-edged fulcrum. The
accuracy achieved by this device was impressive.
These instruments operate in a way similar to that of a seesaw. A sample is placed
on one end of the balance and then adding known weight to the other end until
the beam balances.
2007 PROTOTYPE
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3B PART 3
Corpulosity
Translation: “Give me a place to stand
and with a lever I will move the whole
world.” Archimedes is attributed by
many as the person to come up with
the law of the lever.
3
Mass is the amount of material of which an object is made and is measured by using a
balance. The balance allows us to compare an unknown amount ofmatter to a
known amount of matter. When the beam is completely horizontal, the mass
of the objects on both sides is equal. Thus we can determine the mass of an
object. Weight is the pull of gravity on the mass of an object and is measured
on a scale.
Activity Materials per group:
N
N
N
N
N
3 large paperclips
1 ruler with binder holes
Weight set or objects such as washers of known mass
1 copy of Student Data Page (per student)
1 copy of Student Information Page (from class set)
Activity Instructions:
Ë
Ë
Ë
Ë
1. Gather the materials for your group.
2. Open the paper clips in such a way that you form a shape
as shown in Figure 2 Open the Paperclips. You’ll notice that
when the paper clip now has a “flat top” and a “hook” on
the bottom portion.
3. You will notice that your ruler has holes in it. Take one of
the open paper clips and slip in through one of the holes
at an end on the ruler. The flat portion of the paper clip
rests on the ruler.
Figure 2 –
Open the Paperclips
4. Repeat this procedure with another paper clip; only slip it in the hole in the middle
of the ruler. Again, the top flat portion of the paper clip rests on the ruler.
5. Repeat this procedure with the third paper clip; only slip it in the farthest hole at the
other end of the ruler. The top flat portion of the paper clip should rest on the ruler.
2007 PROTOTYPE
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3B PART 3
Corpulosity
Ë
4
Ë
6. Hold the ruler up by the middle paper clip. You have made an equal arm balance!
The ruler should be close to level. If it isn’t you need to make sure the
paper clips on either end are in the correct holes.
See Figure 3 Equal Arm Balance.
Paper Clips
Figure 3 Equal Arm Balance
Ë
7. For practice in using the equal arm balance you just made, use the weight set or
washers to determine the mass of two objects on your desk.
8. Save your Equal Arm Balance for the next section of the activity.
2007 PROTOTYPE
Positively Aging®/M.O.R.E.
2007©The University of Texas Health Science Center at San Antonio
LESSON 3
ACTIVITY 3B PART 3
Corpulosity
Ë
5