Wednesday (Sep 23):

 Concepts: Review for test tomorrow & Finish film:

 

Journal: What is the Kinetic Theory of Matter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1. KE of a particle = energy of its motion

2. Molecules of all substances are in constant motion

 

 

 

 

 

 

Thurs/Fri    30Sep/1 Oct Library ( Key scientists)

 

 L#7:  1-3, 7 - 14, 17   Due Mon 27 Sep (Motion & Avg Acceleration)

 L #8: 1- 7, 12, 15, 18    Due Wed 29 Sep  (Friction)

L #10: 1- 3, 7 - 10, 14, 17    Due Mon 4 Oct (Motion Graphs)

L #11:  1- 4, 9, 11,  13, 15, 18 Due Wed 6 Oct (Newton's 2nd & 3rd)

L #14:  1- 3, 5, 10, 11, 14 Due Mon 11 Oct  (Free Body)  

 

 

 

 

 

 

 

 

Key Concept(s) Today:  1st Law & Force

Newton’s Three Laws Learning Objectives:

  • Differentiate between mass and weight and the relationship with gravity
  • Differentiate between force, displacement, distance, inertia, speed, velocity and  acceleration.
  • Be aware of major historical individuals and their contribution to the concept of motion.
  • Demonstrate proficiency in solving problems using displacement, distance, inertia, speed, velocity and average acceleration.
  • Measure and describe the sum of all the forces acting on an object.
  • Analyze the effects of balanced and unbalanced forces on the motion of an object
  • Predict & analyze motion of an object based on inertia and forces (balanced and unbalanced)
  • Describe and analyze how forces (contact & field) interact between objects
  • Analyze how physical, conceptual, and/or mathematical models represents and are used to investigate objects, events, systems and processes.  
  • Demonstrate understanding of Free Body Diagrams by drawing Free Body diagrams for static, constant velocity and accelerated motion for single bodies and multiple attached bodies.
  • Demonstrate proficiency in solving problems using Newton’s 1st, 2nd, & 3rd, Laws of Motion
  • Generate and evaluate questions that can be answered through scientific investigations.
  • Apply understanding by planning, conducting, reporting and evaluating  systematic and complex scientific investigations of objects, events, systems, and/or processes.
  • Revised a scientific explanation using additional/new evidence, data, and inferential logic.  
  • Analyze local, regional, national, or global problems or challenges in which scientific design, technology or engineering can be or has been used to find a solution.

 

 

Journal:

1. Why isn't everything (you, your dog, the air, etc.) on the Earth flung off into space as the Earth rotates at such a high speed? Explain

 

2. When you jump up into the air, why do you land in the same spot since the Earth is moving at enormous speed underneath you? Explain

3. What is a force?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1. Gravity is stronger than the inertia that would throw us off the earth.

2. Inertia with both you and the air above you (atmosphere). All is moving together, like we are in a bus or airplane that is moving.

3.

"A force is an interaction between two (material) objects involving a push or a pull."

 

First, a force is an "interaction".

  1. To have a force, you have to have 2 objects - one object pushes, the other gets pushed . In the definition, "(material) objects" means that both objects have to be made out of matter - atoms and molecules. They both have to be "things", in the sense that a chair is a "thing".
  2. A force is something that happens between 2 objects. It is not an independently existing "thing" (object)

 

Let's think about this clearly and simply.

First, forces require:

  1. a push or pull,
  2. an object getting pushed or pulled,
  3. and an object doing the pushing or pulling

 

 

 

 

 

 

 

Notes:

Newton's 1 law

 

Re-state Newton's First Law in your own way / different way / own words

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. "Every object continues in its state of rest, or of motion in a straight line at constant speed, unless it is compelled to change that state by forces exerted on it." (Hewitt, Paul G., Conceptual Physics, Second Edition, p. 28)
     
  2. "Things tend to keep on doing what they're already doing." (Hewitt, p. 29)
     
  3. An object at rest tends to stay at rest, an object in motion tends to stay in motion.
     
  4. Objects resist accelerations.
     
  5. Objects don't like to accelerate.
     
  6. Left to themselves, objects don't speed up, don't slow down, and don't change direction.
     
  7. It requires an unbalanced force to change the velocity of an object.
     
  8. An object at rest will stay at rest unless an unbalanced force acts on it. An object in motion will move at constant velocity unless an unbalanced force acts on it.
     
  9. If an object has a constant velocity, then no unbalanced forces are pushing on it.
     
  10. A force on an object tends to change its velocity. If no force pushes or pulls on an object (or if the forces on the object cancel each other out) then the object's velocity stays the same.
     
  11. No unbalanced force means no acceleration.
     
  12. No force means no acceleration.
     
  13. If no forces act on an object (or if all of the forces that do act cancel each other out), then the object will not:
    • speed up
    • slow down
    • change directions
       
  14. "Whatever an object is doing, that's what it wants to do." - Professor Julius Sumner Miller
     
  15. Objects don't accelerate unless "forced" to.
     
  16. Objects don't change their velocity by themselves.
     
  17. If an object is not accelerating, then either:
    • no forces are pushing on it, or
    • all of the forces that are pushing on it balance each other exactly.
       
  18. If you see an object at rest, or moving in a straight line at constant speed, then you can conclude that either no forces are pushing on the object, or (more likely) all of the forces that are pushing or pulling on the object cancel each other out.
     
  19. If no force acts on a body, we can always find a reference frame in which that body has no acceleration. (Halliday, Resnick, & Walker, Fundamentals of Physics, 5th Edition; p. 82)
     
  20. If nothing pushes on you, you won't accelerate (or decelerate, either).
     
  21. If you leave an object at rest, it will "stay put" forever unless something pushes or pulls on it. If you start an object moving, it will keep moving at the same speed in the same direction forever unless something pushes or pulls on it.
     
  22. "The velocity of a free body is constant in time." (David Layzer, Constructing the Universe, Scientific American Library)
     
  23. Objects continue to do what they are doing unless acted upon by an outside force
     
  24. If Fnet = 0, then a = 0.
     
  25. If there is no net force on an object it is in equilibrium, and vice versa.
     
  26. Objects made of matter have inertia.
     
  27. Inertia is a property of matter.
     
  28. Objects like to be in equilibrium.
     
  29. "Things keep doin' what they're doin' 'til you mess with 'em." - David Charles Schaller
     
  30. If an object doesn't interact with any other objects, it won't accelerate.
     
  31. "A body at rest will remain at rest until 8:45 PM the night before the big project is due, at which point the body will come rushing to the body's parents, who are already in their pajamas, and shout, 'I JUST REMEMBERED THE BIG PROJECT IS DUE TOMORROW AND WE GOTTA GO TO THE STORE RIGHT NOW!'" -

     

 

 

 

 

Riding in a Car

The common experience of riding in a car provides some excellent examples of Newton's First Law in action.

 

Accelerating from Rest - "G Forces"

 

Situation:

Your car is at rest. Suddenly you push down on the "accelerator" and the car accelerates forward. You feel that you are pushed back into your seat.

Common Explanation:

"G Forces," caused by the acceleration, push you back into your seat.

 

Is this Correct or Incorrect Explanation - explain

 

 

 

 

 

 

Problems with the Common Explanation:

First of all, there is nothing pushing you back in your seat! (Acceleration is a concept, not an object, and only objects can push you.  Force... )

Correct Explanation:

You were at rest, so you remain at rest. The car accelerates forward, and you stay where you are.

 

Decelerating - Being "Thrown Forward"

 

Situation:

You are moving at constant velocity (constant speed in a straight line). Suddenly you apply the brakes. You feel "thrown forward" into the dashboard!

Common Explanation:

You are thrown forward.

Is this Correct or Incorrect Explanation - explain

 

 

 

 

 

 

 

Problems with the Common Explanation:

What throws you?

Correct Explanation:

You are moving with a constant velocity. You keep that velocity (while the car slows down) until something stops you.

 

 

Turning - "Centrifugal Force"

Situation:

You go around a curve (at constant speed). You feel pulled toward the outside of the curve.

Common Explanation:

The "centrifugal force" pulls you to the outside of the curve.

Is this Correct or Incorrect Explanation - explain

 

 

 

 

 

 

 

 

 

Problems with the Common Explanation:

: What exerts this "centrifugal force"?

Correct Explanation:

You were moving with a constant velocity (straight line at constant speed). The car turned, and you didn't (since Newton's First Law says your velocity stays the same unless an unbalanced force acts on you.)

 

 

 

 

 

 

 L#5:  1-15, 20   Due Today Wed 23 Sep (Vectors & Forces)

 

 L#7:  1-3, 7 - 14, 17   Due Friday 25 Sep (Motion & Avg Acceleration)

 L #8: 1- 7, 12, 15, 18    Due Monday 28 Sep  (Friction)

L #10: 1- 3, 7 - 10, 14, 17    Due Wed 30 Sep (Motion Graphs)

L #11:  1- 4, 9, 11,  13, 15, 18 Due Monday 5 Oct (Newton's 2nd & 3rd)

L #14:  1- 3, 5, 10, 11, 14 Due Wed 7 Oct  (Free Body)  

 

 

 

 

 

 

Lab Format (09-10)    

Turn in Lab book the next day/period after lab:

 

1.     Hypothesis:

1.      Prediction: Tell how/in which way does the Manipulative Variable (MV) affect the Responding Variable (RV)

 

2.      Give Reason:    Why does MV affect the RV

 

2.     Material used (especially all equipment used to measure)

 

3.     Procedures: (at least 5 steps making sure that you include “record data” and “repeat steps ----“)

 

4.     Data (in table form – showing how MV changes-effects RV)

 

5.     Conclusion:

1.      Was your Hypothesis correct or not.

2.      Use Supporting Data (use limits – high & low average results from MV)

3.       Relationship between MV and RV

Five general questions added to your conclusion

4.      Know the Goal(s): What goals, concepts or standards was this lab trying to achieve?

5.      Evaluate Errors: Explain where you may have experienced possible errors ( & ways to correct them).

6.      Relationship of science & World: Did this lab (concepts) relate to other fields of science? How is this concept(s) being used in the world today? Give examples.

7.      Extension: What future experiment would you like to do in order to further investigate the concept of this lab? Short explanation

8.      Learning: What did you learned or better understand after doing this Lab. (Look at 1st question again)

 

 

 

 

 

 

 

 

Forces Don't Keep Objects Moving

Isaac Newton built on Galileo's thoughts about motion. Newton's first law of motion declares that a force is not needed to keep an object in motion. Slide a book across a table. It does not come to a rest position because of the absence of a force; rather it is the presence of a force - that force being the force of friction. If no force of friction, the book would continue in motion with the same speed and direction - forever! (Or at least to the end of the table top.)

 

 

 

Mass as a Measure of the Amount of Inertia

All objects resist changes in their state of motion. Its called inertia.  The tendency of an object to resist changes in its state of motion varies with mass. Mass is that quantity which is solely dependent upon the inertia of an object. The more inertia which an object has, the more mass it has. A more massive object has a greater tendency to resist changes in its state of motion.

 

 

 

 

 

Do you get it Q's

1. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock will

a. gradually stop.

b. continue in motion in the same direction at constant speed.

 

2. A 2-kg object is moving horizontally with a speed of 4 m/s. How much force is required to keep the object moving at this speed and in this direction?

 

3. Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.

 

4. Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food. What effect (if any) does this practice have upon his inertia? Explain.

 

 

 

6. Ben Tooclose is being chased through the woods by a bull moose which he was attempting to photograph. The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he will be able to use the large mass of the moose to his own advantage. Explain this in terms of inertia and Newton's first law of motion.

 

 

 

 

 

  1. define force.
  2. ...find the net force acting on an object if:
    1. no forces push/pull on it.
    2. 1 force pushes/pulls on it.
    3. 2 forces push/pull on it in the same direction.
    4. 2 forces push/pull on it in opposite directions.
  3. ... state Newton's First Law.
  4. ... define inertia.
  5. ... identify the conditions necessary for a body to be in equilibrium, and describe all of the forces acting on the body.
  6. ... correctly apply Newton's First Law and the concept of inertia to explain various motions, such as the motion of a person inside an accelerating car.

Possible Preconceptions to Correct:

Do you believe that any of the following statements are true? They AREN'T! When you finish Chapter 4, you should understand that each of these statements is FALSE, and WHY it is false .

 

 

    • strings above and below hanging weigh - demonstrates both parts of the 1st Law

 

Purpose:

To demonstrate the "objects at rest" part of Newton's First Law.

Equipment:

3 pieces of chalk and a narrow strip of paper

Description:

Place the strip of paper so at least half of it hangs over the edge of a table. Stand the chalk on end on the paper. Holding the free end of the paper, deliver a sharp blow between the end of the paper and the edge of the table with your free hand.

Explanation:

This is similar to, but not as impressive as, the TableCloth Demo.

 

 

 

Key Concept's) Today: Start Newton's 2nd Law & Free Body Diagrams

 

 

Newton’s Three Laws Learning Objectives:

  • Differentiate between mass and weight and the relationship with gravity
  • Differentiate between force, displacement, distance, inertia, speed, velocity and  acceleration.
  • Be aware of major historical individuals and their contribution to the concept of motion.
  • Demonstrate proficiency in solving problems using displacement, distance, inertia, speed, velocity and average acceleration.
  • Measure and describe the sum of all the forces acting on an object.
  • Analyze the effects of balanced and unbalanced forces on the motion of an object
  • Predict & analyze motion of an object based on inertia and forces (balanced and unbalanced)
  • Describe and analyze how forces (contact & field) interact between objects
  • Analyze how physical, conceptual, and/or mathematical models represents and are used to investigate objects, events, systems and processes.  
  • Demonstrate understanding of Free Body Diagrams by drawing Free Body diagrams for static, constant velocity and accelerated motion for single bodies and multiple attached bodies.
  • Demonstrate proficiency in solving problems using Newton’s 1st, 2nd, & 3rd, Laws of Motion
  • Generate and evaluate questions that can be answered through scientific investigations.
  • Apply understanding by planning, conducting, reporting and evaluating  systematic and complex scientific investigations of objects, events, systems, and/or processes.
  • Revised a scientific explanation using additional/new evidence, data, and inferential logic.  
  • Analyze local, regional, national, or global problems or challenges in which scientific design, technology or engineering can be or has been used to find a solution.

 

Journal:

1. State Newton's 2nd Law ......

 

2. Define:

a. Force

b. Net Force

c. Normal Force

d. Tension

e. Unbalanced forces

f. Balanced forces

g. Equilibrium

 

 

 

 

 

 L#5:  1-15, 21   Due Today Wed 23 Sep (Vectors & Forces)

 

 L#7:  1-3, 7 - 14, 17   Due Friday 25 Sep (Motion & Avg Acceleration)

 L #8: 1- 7, 12, 15, 18    Due Monday 28 Sep  (Friction)

L #10: 1- 3, 7 - 10, 14, 17    Due Wed 30 Sep (Motion Graphs)

L #11:  1- 4, 9, 11,  13, 15, 18 Due Friday 2 Oct (Newton's 2nd & 3rd)

L #14:  1- 3, 5, 10, 11, 14 Due Monday 5 Oct  (Free Body)  

 

 

Notes

Force: Push or Pull between TWO objects:

 

Contact Forces:  

  • Normal - (Push always & 900 from surface
  •   sometimes called Applied (or normal) if not from below                               (Push always & 900 from surface)
  • Tension -  (Pull always)
  • Buoyancy  (push up)
  • Friction (push against)
  • Force of Air or Drag (Air Friction)

Non-contact Forces

  • Gravitational Force (Pull always called Weight = Mass x Gravity)

  • Magnetism  (push or pull)

  • Electric  (push or pull)

 

 

 

 

 

Free Body Diagram:  Means one object free from all other things except the forces on it. ( i.e., show only the forces acting on the object)  

 

  • A book is at rest on a table top. A free-body diagram for this situation looks like this:
     

 

 

2. A girl is suspended motionless from the ceiling by two ropes. A free-body diagram for this situation looks like this:
 

 

3. An egg is free-falling from a nest in a tree. Neglect air resistance. A free-body diagram for this situation looks like this:

 

 

4. A flying squirrel is gliding (no wing flaps) from a tree to the ground at constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:
 

 

 

5. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:
 

 

 

6. A rightward force is applied to a book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. A free-body diagram for this situation looks like this:

 

 

 

7. A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder. A free-body diagram for this situation looks like this:

 

 

 

8. A skydiver is descending with a constant velocity. Consider air resistance. A free-body diagram for this situation looks like this:

 

 

 

9. A force is applied to the right to drag a sled across loosely-packed snow with a rightward acceleration. A free-body diagram for this situation looks like this:

 

 

 

10. A football is moving upwards towards its peak after having been booted by the punter. A free-body diagram for this situation looks like this:

 

 

11. A car is coasting to the right and slowing down. A free-body diagram for this situation looks like this:

 

 

 

 

 

        

 

 
No friction, what does the free body diagram look like? 
 
 

 

 

 

 

 

 

 

 

 

 

 

Question 2.