Newton and Copernicus: Lesson #30
2b:Students know when an object is subject to two or more forces at once, the result is the cumulative effect of all the forces.
1: What force causes one side of the balance to tip down and pushes the other side up?
2: In your own words, explain how you think a double pan balance works.
3: If C = the mass of Copernicus and N = the mass of Newton, which of these is correct?
C – N < 20g
C - N > 20g
C – N = 20g
4: The circles (thought bubble) in the last frame indicate that Copernicus is “thinking”
something. Why does he hesitate to say what he is thinking out loud?
5: If Copernicus is having fun, it’s because he’s associating the pan balance with a piece of
playground equipment. What piece of playground equipment works the same way as the
double pan balance?
A Newton and Copernicus Companion: Copyright August 2007, J.C. Olson, www.newtonandcopernicus.com
Newton and Copernicus: Lesson #30
CSS: grade8: #2b:Students know when an object is subject to two or more
forces at once, the result is the cumulative effect of all the forces.
LESSON GUIDE:
Vocabulary: hesitate, associate
Academic Vocabulary: gravity, pan balance,
A: Have your students read the comic strip silently and carefully observe the background of
the drawing to look for supporting information. (V)
B: Have them read through the questions and circle the number of each question they believe
they can answer correctly.
Pair/Share.
C: Reading aloud. One student reads Newton’s lines, the other reads Copernicus’s lines.
Switch roles and repeat. (A)
D: The pair discusses questions 1- 5 the each student draws a box around the number (or
circled number) of each question they believe they can answer correctly.
E: Call on students to come up front and dramatically read or act out the comic strip. Supply
props to represent the background information in the strip. (20g mass) (K)
F: Whole group: Have students share what they see in the drawings that supports the dialog.
G: Students individually write out their responses to questions 1-5.
Answers for 1-5
1: Gravity
2: Gravity pulls on both sides of the balance, but a heavier (more massive) object applies a
stronger downward force on the balance, pushing the other side up. (see background info)
3: C – N < 20g: The difference between the masses of the two rats must be less than 20,
Otherwise the balance would not tip in the other direction when the mass is added or
removed.
4: Newton plans to repeat the demonstration. If Copernicus says he gets it, Newton will stop
and the ride will be over.
5: An old fashioned piece of playground equipment called a teeter totter.
Background information for pushing the envelope.
(The greater mass on one side is pulled down (falls) by gravity, the pan balance pushes up
against it. The torque of larger mass working through the fulcrum of the 1st class lever
pushes the opposing pan against the lesser mass. (The upward push of the pan overcomes the
force of gravity on the opposing side.) Gravity works against itself when masses are unequal.
A Newton and Copernicus Companion: Copyright August 2007, J.C. Olson, www.newtonandcopernicus.com