Wednesday Jan' 28

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Wednesday (Jan. 28) Several groups finished the
assignments about 40 minutes before the end of
the class period. Any students in these groups
felt being rushed to get done quickly?

Several groups finished a few minutes
just before the end of the class period. Any
student in these group felt being dragged by the
other group members? Please send me an e-mail to
voice your feeling/opinions. huang001_at_umn.edu
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Summarizing Questions 1-51 1. Similarities and
differences between contact interactions that
involve elastic objects and those that involve
only rigid objects.
2. The contact interactions in this activity
What two types of energy changed in the objects?
What is the evidence for these energy changes?
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3. Contact interaction involving elastic objects
what type of energy transferred between the
two objects? What evidence supports this idea?
4. Complete S/R energy diagram for the contact
interaction in which the cart slowed down
as it ran into the rubber band.
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5. Experiment 1 You held a cart against a
rubber band before letting go to lunch it.
Do you think there was a contact interaction
between the cart and the rubber band even
while you were holding the cart? If so, why
did the speed of the cart not change until
after you let go? If not, why not?
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Finish page 1-68, then we will have break
immediately. Resume the class at 155
PM Discuss the Summarizing Questions, 1-64 S1
group 6 S2 group 7 S3 group 1 S4 group
2 S5 group 3 S6 group 4 S7 group 5 S8
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Summarizing Questions 1-64 1. Moving objects tend
to slow and stop eventually. Do you think
this behavior is due to an interaction, or
does it just happen naturally? Does the
kinetic energy just disappear, or does
something else happen to it?
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2. Similarities and differences between
friction-type contact interactions and the
other types of contact interaction you
examined in previous activities?
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3. Complete the S/R energy diagram. The cart
slows down gradually as it moves along the track.
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4. Simulation vs. Real Experiment Why do you
think you used the simulator model in the
final stages of this experiment, rather than
the real cart and track?
5. Three different types of contact interactions
Wile watching a moving object, what evidence
would you look for to tell you that it is
currently involved in a contact interaction
of any type?
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6. Does the contact interaction seem to last over
a period of time or does it only happen
at a single instant in time? Give evidence
from the activities in this chapter.
7. Quick push an object and leave it alone,
free of any contact interactions. After
initial push, it would speed up, slow down,
or constant speed? Your reasoning.
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8. How the speeds of objects change when
they are involved in a contact interaction?
John ? Sandy?
John
Sandy
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Rug Burn
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• Summarizing Questions 1-83
• In what way(s) are the heat-conduction
• and infrared interaction similar?
• In what way(s) are they different?

2. Invent an example of a heat-conduction
interaction or an IR interaction different
from the ones discussed in the
activity. Draw the S/R energy diagram to describe
the interaction.
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3. If two objects are at the same temperature,
can heat energy be transferred from one to the
other? Why?
4. Warm sodas in a cooler full of ice.
Scientific explanation. Why a can of soda cools
down when in contact with the ice?
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Energy diagram
narrative