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Introduction Who is the audience? 8 th grade Physical Science Objective This project will allow students to learn to solve logic and mathematical problems involving motion and forces in an electronic environment.

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Motion and Forces Motion is defined as the change in position of an object. Question: Question: If an object is observed to be in the same position two distinctly different times, do you know enough to determine whether it was in motion at any point during this time? YES NO

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Motion and Forces Motion is defined as the change in position of an object. Question: If an object is observed to be in the same position two distinctly different times, do you know enough to determine whether it was in motion at any point during this time? Incorrect!

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Motion and Forces Motion is defined as the change in position of an object. : Question: If an object is observed to be in the same position two distinctly different times, do you know enough to determine whether it was in motion at any point during this time? Correct!

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Motion and Forces Motion is measured through the quantities of Speed, Velocity, and Acceleration.

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Motion and Forces Speed measurement of how fast position changes. The units of measurement for Speed are meters per second, or m/s. Speed is a scalar quantity, or a quantity with just magnitude or size. Velocity measurement of how fast position changes in a specific direction. The units of measurement for velocity are meters per second East, North, up, down, left, etc., or m/s East. Also, direction can be noted with the use of an arrow ( ). Velocity is a vector quantity, a quantity with both magnitude and direction.Acceleration measurement of how fast velocity changes. The unit of measurement for acceleration is the meter per second per second, or m/s 2. Acceleration is also a vector quantity though not represented by an arrow or direction per se, rather as a positive (+) or negative (-) acceleration.

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Motion and Forces Mathematically, speed is the quotient of distance over time, or S = d/t In the animation below, the “mouse-surfer” travels an approximate distance of 23 centimeters in five seconds. So, applying the formula above we determine the surfer to have a speed of 4.6 cm/s. S = d/t = 23 cm/5 s = 4.6 cm/s 23 centimeters

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Motion and Forces Solve: A wheelchair racer completes a 100-meter course in twenty seconds. What is her speed? a)5 m/s a)5 m/s b)10 m/s b)10 m/s c)15 m/s c)15 m/s d)20 m/s d)20 m/s

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Motion and Forces Solve: A wheelchair racer completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer completes a 100-meter course in twenty seconds. What is her speed? Correct!

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Motion and Forces Mathematically, velocity is similar to speed. However, you must denote the direction of travel for the object in question v = d/t, In the animation below, the “mouse-surfer” travels an approximate distance of 23 centimeters in five seconds. So, applying the formula above we determine the surfer to have a speed of 4.6 cm/s. The length of the arrow is proportional to the magnitude of the velocity. A greater velocity would result in a larger arrow, a lesser velocity would result in a smaller arrow. 23 centimeters

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Motion and Forces Solve: A wheelchair racer travelling North completes a 100-meter course in twenty seconds. What is her speed? a)5 m/s a)5 m/s b)5 m/s, East b)5 m/s, East c)5 m/s, South c)5 m/s, South d)5 m/s, North d)5 m/s, North

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Motion and Forces Solve: A wheelchair racer travelling North completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer travelling North completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer travelling North completes a 100-meter course in twenty seconds. What is her speed? Incorrect!

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Motion and Forces Solve: A wheelchair racer travelling North completes a 100-meter course in twenty seconds. What is her speed? Correct!

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Motion and Forces Mathematically, acceleration is the quotient of the change in velocity and the change in time. a = ∆v / ∆t = (v f – v i ) / (t f – t i ) = (final velocity – initial velocity)/(final time – initial time) A change in velocity denotes a change in speed, a change in direction, or a change in both speed and direction. For instance, a car accelerating from rest to 15 m/s over five seconds is an example of an accelerating object. Also, a car maintaining a constant speed, say 5 m/s, while driving around a circular track is also an example of an accelerating object. Finally, a car reducing speed while rounding a corner and increasing speed out of the corner is also an example of an accelerating object.

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Motion and Forces Solve: A cheetah can go from 0 m/s, rest, to 20 m/s in 2 seconds. What is the cheetah’s acceleration? a)- 10 m/s 2 a)- 10 m/s 2 b)10 m/s 2 b)10 m/s 2 c)- 40 m/s 2 c)- 40 m/s 2 d) 40 m/s 2 d) 40 m/s 2

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Motion and Forces Solve: A cheetah can go from 0 m/s, rest, to 20 m/s in 2 seconds. What is the cheetah’s acceleration? Incorrect!

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Motion and Forces Solve: A cheetah can go from 0 m/s, rest, to 20 m/s in 2 seconds. What is the cheetah’s acceleration? Incorrect!

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Motion and Forces Solve: A cheetah can go from 0 m/s, rest, to 20 m/s in 2 seconds. What is the cheetah’s acceleration? Incorrect!

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Motion and Forces Solve: A cheetah can go from 0 m/s, rest, to 20 m/s in 2 seconds. What is the cheetah’s acceleration? Correct!

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Motion and Forces A force is simply a push or a pull. Forces cause a change in motion. The unit of measurement for force is the Newton (N). One Newton of force causes a 1-kg mass to accelerate 1 m/s 2. 1 N = 1 (kg. m)/s 2 Additionally, forces are vectors, which means they have magnitude and direction. The size of the vector is proportional to the magnitude of the force. Forces include such physical quantities as magnetism, electricity, gravity, friction, lift, and thrust.

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Motion and Forces Question: An object is observed to be at rest. Moments later the object is observed to be moving away from you, the observer. Has there been a force applied to the object to cause its motion? Yes No

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Motion and Forces Question: An object is observed to be at rest. Moments later the object is observed to be moving away from you, the observer. Has there been a force applied to the object to cause its motion? Incorrect!

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Motion and Forces Question: An object is observed to be at rest. Moments later the object is observed to be moving away from you, the observer. Has there been a force applied to the object to cause its motion? Correct! If an object is in motion it has been acted on by a force.

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Motion and Forces When a force is applied to a mass, the motion of the mass has changed. Newton’s 1 st Law:An object in straight-line motion, or at rest, will remain in straight-line, or at rest, until acted upon by unbalanced outside forces. Inertia is another way of stating Newton’s 1 st Law. The inertia of an object is the object’s resistance to a change in motion. Inertia is strictly dependent on the mass of the object. The more massive an object, the more difficult that object is to move. Therefore, the object has more inertia than a lighter object and will require a greater force to change its motion.

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Motion and Forces Question: Which has more inertia, a 747 jumbo-jet at rest before taxiing to the runway, or a motorcycle travelling 44 meters per second. Jumbo-jet Motorcycle

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Motion and Forces Incorrect!

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Correct! A jumbo-jet has more mass than a motorcycle, therefore more inertia. The speed of the motorcycle is not important until we discuss momentum

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Motion and Forces Force and mass determine acceleration. Newton’s 2 nd Law:The acceleration of an object increases with increased force and decreases with increased mass. Fa F = ma

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Motion and Forces Question: According to Newton’s 2 nd Law, in order to increase the acceleration of an object you must Increase force on the object, or decrease mass of object Decrease force on the object, or increase mass of object

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Motion and Forces Question: According to Newton’s 2 nd Law, in order to increase the acceleration of an object you must Incorrect! Increased mass of the object or decreased force by the person would result in an unfortunate circumstance.

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Motion and Forces Question: According to Newton’s 2 nd Law, in order to increase the acceleration of an object you must Correct! Increased force by the person or decreased mass of the object would yield good results. The rock moves and the person remains alive

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Motion and Forces Forces act in pairs. Newton’s 3 rd Law: Newton’s 3 rd Law:When one object exerts a force on another object, the second object exerts a force equal in magnitude and opposite in direction on the first object. Action+Reaction Interaction

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Motion and Forces According to Newton’s 3 rd Law, an action force and its reaction force are Question: According to Newton’s 3 rd Law, an action force and its reaction force are Equal in magnitude and opposite in direction Equal in size and direction

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Motion and Forces According to Newton’s 3 rd Law, an action force and its reaction force are Question: According to Newton’s 3 rd Law, an action force and its reaction force are Incorrect!

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Motion and Forces The action-reaction pairs are equal in size and opposite in direction. The two yellow vectors are equal in magnitude to the red arrow, but opposite in direction. Otherwise, the jack would accelerate through the car, or the car would come crashing down on the mechanic. Correct! According to Newton’s 3 rd Law, an action force and its reaction force are Question: According to Newton’s 3 rd Law, an action force and its reaction force are

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Motion and Forces You’ve completed your lesson on motion and forces. Congratulations on a job well- done! Created by Rich Edelen, March 2009 Michigan State University Masters Certificate in Educational Technology

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