Mr. Bouyer
Day 1 |
Day 2 |
Day 3 |
Lab |
Vocabulary Test
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- Force
- Friction
- Sliding friction
- Rolling friction
- Fluid friction
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- Aristotle
- Newton
- Balanced forces
- Unbalanced forces
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- Newton's 3 Laws of Motion
- Gravity
- Free fall
- Acceleration of gravity
- Terminal velocity
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Force: any push or pull.
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How does a lubricant reduce friction? |
Forces give energy to objects.
Forces cause a change in motion.
Friction: 
a force that opposes motion.
Types of friction:
- Sliding friction - when two solid surfaces slide over each other.
- Rolling friction - when an object rolls over a surface.
- Fluid friction - when an object moves through a fluid.
Experiment withfriction. 
Satellite Operator
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Aristotle and Newton had different ideas about forces and motion.
Aristotle's idea: 
For an object to move at a constant speed,
a constant force must be applied.
Newton's idea:
An object moving at a constant speed will continue
at that speed without additional force being applied.
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- Friction is not always bad. Discuss this with your table two examples of when friction is good. Tell your science facilitator when you have them.
- Ask your teacher for a ball. Go into the hall and roll (do not throw) the ball down the hall.
- Carefully observe the actions of the ball.
- Do your observations support Aristotle or Newton? Be able to verbally explain the reasoning for your answer.
- With your table, demonstrate each of these for your science facilitator. If you need something other than your textbook, ask for it.
- Move a book across a table in a way that demonstrates sliding friction.
- Move a book across a table in a way that demonstrates rolling friction.
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Day 2
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What two balanced forces are acting on you right now? |
Most of the time an object is being acted on by more than one force.
For instance, there are several forces acting on you sitting in your chair right now.
Balanced forces:
- Forces that are opposite in direction and equal in size.
- Balanced forces cause no change in motion.
Unbalanced forces:
- Forces that are not opposite and equal.
- Unbalanced forces always cause a change in motion.
- A very graphic example of unbalanced forces causing motion.
Newton's Three Laws of Motion explain all aspects of motion.
Newton's First Law describes motion produced by balanced forces.
- An object at rest will remain at rest, and a moving object will remain at a constant velocity unless unbalanced forces act on it.
Newton was first to use the term inertia to describe the tendency of objects to remain in motion or stay at rest. Inertia comes from the Latin word iners, which means "lazy".
Some history behind the first law.
Newton's Second Law describes motion produced by unbalanced forces.
- This law is best stated using the equation:
Force = mass X acceleration
F = m a
Acceleration is always in the direction of the unbalanced force.
The units of force are Newtons.
1 N = 1 kg X 1 m/s/s
1 N = 1 kg . m / s2
Some history behind the second law.
Newton's Third Law explains why forces act in pairs.
- For every action, there is an equal and opposite reaction.
Forces always act in pairs.
Some history behind the third law.
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Practice Problem:
- What force is needed to accelerate an object with a mass of 25000 grams at a rate of 10 m/s2?
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What forces cause a gyroscopeto work?
What makes a rocket enginework?
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In-class Assignment 222:
This assignment must be turned in by the end of class today to receive credit.
Scoring criteria
- List the forces acting on you while sitting in a chair.
- Are the forces acting on you balanced or unbalanced? Give the reasoning for your answer.
- Tell which of Newton's Laws applies to each of these situations.
- The space shuttle leaving the launch pad.
- A small car gets better gas milage than a big car.
- A person walking.
- A person is sitting in a car at a stoplight. Their car is rear-ended by another car giving them whiplash.
- Brakes are applied to a car traveling on an icy road but it does not slow down.
- A hunter shoots a shotgun at a bird and bruises his shoulder.
- What force (in Newtons) is needed to accelerate a one ton (2000 pound) truck at a rate of 50 m/s2?
Hint: use factor label and the following:
454 grams = one pound
1000 grams = one kilogram
Day 3
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Why does a bowling ball fall faster than a feather? |
Gravity: the force of attraction between all objects in the universe.
- Gravity is the weakest of the known natural forces, only becoming obvious when massive objects like stars and planets are involved.
- Gravitational radiation is only 1 X 10 -40 times as strong as electromagnetic radiation.
Free fall - an object falling under the influence of gravity.
- Near the surface of the earth all objects are accelerated by gravity at a rate of 9.8 m/s/s.
- Calculations can be simplified by rounding to 10 m/s2.
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Drop some objectson Earth.
Drop some objects on Earth, Moon, and Mars.
Terminal velocity: the point at which air resistance offsets the weight of a falling object, stopping its acceleration.
The object continues to fall but does not accelerate. A parachute is an example of terminal velocity.
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Read the activity described on this webpage.
Try it with the people at your table.
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Research Links:
Physical Science
Answer to sample problem:
F = ma
F = (25kg) (10m/s2)
F = 250 Newtons
Lubricants reduce friction by changing sliding friction into fluid friction.
Gravity is pulling you down. Your chair is pushing you up. Since you are not moving, these two forces must be balanced.
Gravity accelerates an object downward until air resistance offsets the weight of the object. Air resistance offsets the weight of a falling feather before it offsets the weight of a falling bowling ball.
is an example of terminal velocity.
to make a distance/time graph of this data.
