One physics question and physics observation

1
Plan for todays class

• One physics question and physics observation
• 2. Summarizing Questions, page1-110
• 3. Two demonstrations
• 4. Work on activity 7
• 5. Summarization
• 6. Start chapter 2
• Important announcement Quiz 1 will be on Feb.
  11 (W).
• A practice quiz has been posted on the class
  web-site.

2
Plan for todays class

• One physics question and physics observation
• 2. Summarizing Questions, page1-110
• 3. Two demonstrations
• 4. Work on activity 7
• 5. Summarization
• 6. Start chapter 2
• Important announcement Quiz 1 will be on Feb.
  11 (W).
• A practice quiz has been posted on the class
  web-site.

3
Summarizing Questions, page1-110 S1 Is energy
conserved during a friction-type contact
interaction? What evidence supports your
answer? (2) S2 How is it possible for an
object (like the friction cart in this
activity) to have no energy input during an
interaction yet still have an energy output?
Use your ideas about conservation of energy
to explain your thinking.
(3)
4
Plan for todays class

• One physics question and physics observation
• 2. Summarizing Questions, page1-110
• 3. Two demonstrations
• 4. Work on activity 7
• 5. Break after finishing activity 7
• 6. Discuss explanation 2 after the break (start
  at 155)
• 7. Summary
• 8. Start chapter 2
• Important announcement Quiz 1 will be on Feb.
  11 (W).
• A practice quiz has been posted on the class
  web-site.

5
P 1-113 Explanation 2 Why does a baseball
player slow down as he slides into base?
In a close situation, a baseball player will
usually choose to slide into a base rather
than just run to it. (This gives him the
advantage that he can be safe by just
getting his fingers to the base, rather than his
whole body. It is also more difficult for a
fielder to tag him.) In this explanation we
want you to consider why it is that the
player slows down while he is sliding into base.
(Note that this is a question about while he is
sliding, not about anything he does before
that.) Answering the following questions should
help you in constructing an explanation.
6
Do you think the effects of friction can be
ignored in this situation? Why or why not?
(4) While he is sliding along the ground what,
if anything happens, to the kinetic energy and
thermal energy of the player? Why do you
think so? (5) While he is sliding along the
ground, is there an energy input to the player?
If so, of what type? Explain your thinking.
(6) While he is sliding along the ground are
there any energy outputs from the player? If
so, what type do you think they are and why? (7)
7
Energy I/O diagram (1)
8
P 1-115, Narrative with spaces as in the text.
(2) As the player slides, he is involved in
a(n)__________ interaction with the ground.
During this interaction __________ energy is
transferred from him to the ground and, at the
same time, his __________energy increases. As a
result of this increase in __________energy,
__________energy is transferred from him to his
surroundings. Since there is no energy
_________ to the player, the ________________means
these energy outputs and increases in
_________energy must be accounted for by a
________ in the _________energy of the player.
This decrease in his __________means he
__________ as he slides.
9
Review

• What is the title of chapter 1?

10
Review

• What is the title of chapter 1?
• 2. How many different types of interaction being
  discussed?

11
Review

• What is the title of chapter 1?
• 2. How many different types of interaction being
  discussed?
• 3. How many different types of energy being
  discussed?

12
Review

• What is the title of chapter 1?
• 2. How many different types of interaction being
  discussed?
• 3. How many different types of energy being
  discussed?
• 4. What does the speed vs. time plot tell us?

13
B
C
speed
A
Time
14
Review

• What is the title of chapter 1?
• 2. How many different types of interaction being
  discussed?
• 3. How many different types of energy being
  discussed?
• 4. What does the speed vs. time plot tell us?
• 5. Force change in speed vs. time
  energy change

15
Review

• What is the title of chapter 1?
• 2. How many different types of interaction being
  discussed?
• 3. How many different types of energy being
  discussed?
• 4. What does the speed vs. time plot tell us?
• 5. Force change in speed vs. time
  energy change
• 6. Conservation of energy

16
GROUP 1 Chacon,Valerie M Jurrens,Aaron
David Murphy,Molly Elizabeth Salazar,Ashley
Marie GROUP 2 McCullough,Molly
Brenna Ritten,Alison Marie Wappel,Amanda J GROUP
3 Decker,Katelyn Alissa Zacharias,Samantha
Shea Holgers,Angela C GROUP 4 Brick,Jennifer
Rosemary Dressen,Brianna Rose Holter,Emily
Rose Thorson,Kathryn JoAnne
GROUP 5 Roberts,Vanessa Anita Heim,Kelli
Marie Johnson,Ashlee Rene Loe,Emily Anne GROUP
6 Souknhindy,Shanna Marie Dorschner,Marissa
Anne Thoemke,Marie Lynn GROUP 7 Poeschl,Jessica
M Titrud,Melissa Jane Le,Hai Truong
17
Plan for todays class

• One physics question and physics observation
• 2. Summarizing Questions, page1-110
• 3. Two demonstrations
• 4. Work on activity 7
• 5. Break after finishing activity 7
• 6. Discuss explanation 2 after the break (start
  at 155)
• 7. Summary
• 8. Start chapter 2
• 9. At 245 PM, discuss the initial ideas p2-4 to
  2-5
• Important announcement Quiz 1 will be on Feb.
  11 (W).
• A practice quiz has been posted on the class
  web-site.

18
Initial idea, P 2-4 to p 2-5 Think about a soccer
player kicking a stationary ball. As he
interacts with it, by kicking it, the ball rolls
across the grass and gradually comes to a halt.
Sketch a speed-time graph for the motion of the
ball. Be sure to include both the motion of the
ball while the players foot is touching it, and
its motion after the foot has lost contact with
it. (4)
19
Using a colored pencil, indicate the period on
the graph during which you think the foot was in
contact with the ball and briefly explain your
reasoning. (5) Using a colored pencil, indicate
the period on the graph during which you think
there was a force pushing the ball forward.
Again, explain your reasoning. (6)
20

• Why do you think the ball gradually slows down
  and
• eventually stops after it has been kicked? (7)
• Now draw two pictures of the ball and use arrows
  to show
• what forces (if any) you think are acting on the
  ball at two
• different times during its motion.
• Label your arrows to show where the forces come
  from.
• During the time foot was in contact with the
  ball. (1)
• ii) After the foot has lost contact and the ball
  is rolling
• across the grass. (2)
• Briefly explain the reasoning behind your
  pictures.

21
Plan for todays class

• One physics question and physics observation
• 2. Summarizing Questions, page1-110
• 3. Two demonstrations
• 4. Work on activity 7
• 5. Break after finishing activity 7
• 6. Discuss explanation 2 after the break (start
  at 155)
• 7. Summary
• 8. Start chapter 2
• 9. At 245 PM, discuss the initial ideas p2-4 to
  2-5
• Important announcement Quiz 1 will be on Feb.
  11 (W).
• A practice quiz has been posted on the class
  web-site.

22
S/Q, P 2-13 S1 While the hand is exerting a
force on the cart, what is the motion of the
cart like? What evidence from this activity
supports your idea? S2 Do you think the force
from the hand was transferred from the hand
to the cart during this interaction between
them, and then continued to act on it after
contact was lost? What evidence supports your
idea?
23
S3 At what moment do you think the force of the
hand stopped acting on the cart? S4
During a contact interaction, what do you think
is transferred from the source to the
receiver energy, force both, or neither?
Explain your reasoning.
24
P 2-15 to P 2-16, Initial idea Imagine you had a
low friction cart at rest at one end of the
track in front of you. Now, suppose you were to
interact with it by pushing the cart
continuously from behind with a
constant-strength push. What do you think the
motion of the cart would be like under these
circumstances? Sketch a speed-time graph to
illustrate you idea. Briefly explain your
reasoning.