Download Newton`s Laws of Motion Section 1 Motion A. Motion is a change in

Newton’s Laws of Motion
Section 1 Motion
A. Motion is a change in position.
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Distance – the entire path an object travels
The distance and direction between starting and stopping positions is displacement.
Relative motion and object’s position change is described in terms of a reference point
B. Speed- distance traveled divided by the time needed to travel the distance, or
speed =distance
time
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Constant- speed is the same at any given moment in time
 Speed at a particular instant in time is changing/instantaneous speed
C. Velocity- displacement divided by time, or v =
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Formula calculates average velocity.
Includes concept of direction as well as speed
D. Change in velocity divided by the time required for the change to occur is acceleration.
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Acceleration occurs when an object slows down as well as speeds up.
A change in speed can be used to calculate acceleration.
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Acceleration is final speed minus initial speed divided by time,
or acceleration = final speed – initial speed
time
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Initial speed is zero objects at rest
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Turning or changing direction is also acceleration.
Section 2 Newton’s First Law
A. Laws of motion are sets of rules first stated by Isaac Newton.
1. Force - a push or pull with a size and direction
2. Contact force involves objects touching each other.
3. Long-range forces include gravity, magnetism, and electricity.
4. When scientists measure force, they use the Newton , abbreviated N.
B. 1st---____ law of motion- an object will remain at rest or move in a straight line with constant speed unless a force
acts on it.
1. Inertia measures an object’s tendency to remain at rest or keep moving.
2. Inertia is related to mass ; objects with more mass have more inertia.
C. Adding forces- sometimes more than one force acts on an object
1. Balanced forces-forces that are equal but in opposite directions, canceling
each other
2. If one force is greater than another, a change in motion will result from the
unbalanced forces.
3. An object acted on by an unbalanced force changes velocity.
Section 3 Newton’s Second Law
A. Second law of motion- an object acted on by an unbalanved force will accelerate in the direction of the force.
1. Acceleration equals force divided by mass, or a = force
mass
2. Force is equal to the combination of all forces, or the total force that acts on an
object.
B. Second law can also be used to find force if mass and acceleration are known.
1. Near Earth’s surface, the force of gravity causes all objects to fall with the same
acceleration -9.8 m/s.
a. For any object that is falling, the force of gravity equals mass times
acceleration due to gravity, or F = m x (9.8 m/s.)
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Because weight is the force of gravity on an object, an object’s weight equals mass times acceleration due to
gravity, or weight = m x (9.8 m/s.)
2. Weight and mass are not the same thing.
a. Weight changes when the acceleration due to gravity changes.
b. Mass remains the same no matter what weight is
C. Friction - a force that resists motion and is always present between two moving surfaces.
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Static friction- keeps a stationary object from moving on a surface when a force is applied to the object
Sliding friction- occurs when two surfaces slide past each other; slows down the moving object
Rolling friction- friction between a surface and a wheel turns a wheel.
Air resistance – typical action of air molecules on a forward-moving object, slowing its motion.
Section 4 Newton’s Third Law
A. Third law of motion- forces always act in equal but opposite pairs
1. When a force is exerted on an object, the object exerts the same amount of force.
2. Third law of motion applies whether forces are contact or long-range .
B. Things move because action and reaction forces work on different objects.
1. Friction is a factor in the third law.
2. Using the second law equation, the object with the larger mass has the smaller
acceleration if the same force is applied.
3. All objects in the universe exert a force on all others; however, differences in
mass may make these forces unnoticeable.
C. The three laws of motion describe how any object moves when forces act on it.