Motion Notes

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Motion Notes
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Measurement

• A measurement is a quantity with a unit that
  tells what time the quantity means.
• For example
• 3 seconds is a measurement of time that includes
  a quantity ( 3 ) and a unit (seconds).
• A quantity is a number.
• A unit is a

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Units for Motion

• Length (Distance)
• Milimeters
• Meters
• Kilimeters
• Time
• Seconds
• Minutes
• hours

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MOTION

• Motion change in your position compared to a
  frame of reference.
• as a train moves past a platform, people on the
  platform see those on the train speeding by. when
  people on the train look at one another, they
  don't seem to be moving at all OR moving
  backwards

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MOTION

• frame of reference - comparing an objects
  motion to another object
• Your house stays still as the cars drive past
• a frame of reference is necessary in order to
  describe motion

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• Speed distance traveled per unit of time
• S d/t
• A car travels 70 km per hour
• Choose units that make sense m/s, km/h

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Formulas
S
D
T
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MOTION

• Distance the length of a path between two points.
  
• GO METRIC km, m, mm, cm, etc.

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Time

• the measured or measurable period during which an
  action, process, or condition exists or continues
  duration.

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• Average speed- the total distance traveled, d,
  divided by the total time, t, it takes to travel
  that distance.
• speed distance/time
• Ex- on vacation 60 km in 0.8 hr, and 35 km in
  0.5 hr. What is your average speed?

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• Instantaneous speed the rate at which an object
  is moving at a given moment in time
• Speedometer in a car
• Average speed is computed for the entire
  duration of a trip, and instantaneous speed is
  measured at a particular instant.

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Graphing Motion

• The slope of a line on a distance-time graph is
  speed.

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Velocity

• Velocity- the speed and direction in which an
  object is moving
• Sometimes you need to know the directionIf two
  trains are traveling
• Velocity is a vector.

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Acceleration

• Acceleration-The rate of change in velocity
• Changes in speed, direction or both
• Can Increase or decrease, (be positive or
  negative)
• acceleration zero if it is moving at the same
  speed in thesame direction

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• Constant acceleration is a steady change in
  velocity over time.
• the velocity of the object changes by the same
  amount each second
• A jet taking off.

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Calculating Acceleration

• Vf final velocity
• Vi initial (starting) velocity

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Graphing Acceleration

• The slope of a speed-time graph is acceleration

Can be linear or non linear graph
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76 77 I will be able to investigate the
effect of speed on the severity of a collision.

• Vocabulary
• Acceleration
• Force
• Balanced force
• Unbalanced force
• Net force
• Speed
• Momentum
• Conservation of momentum

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Force

• force is a push or a pull that acts on an object.
   
• can cause a resting object to move
• can accelerate a moving object (change in ____
  ____)

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• Newtons(N)- measurement of force
• One N is the force that causes 1-kilogram (mass)
  to accelerate at a rate of 1 meter per second
  each second (1 m/s2).
• Unit for force(1 N 1 kgm/s2)

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FORCE

• Balanced force- when forces are balanced, net
  force 0. No change in motion (arm wrestle)
• Unbalanced force- causes object to accelerate

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FORCE

• NET FORCE - Combine forces in the same direction,
  (subtract in opposite direction)
• Ex. If two people are pushing a cart at the same
  time, you would combine.
• In a tug of war, the two forces would be
  subtracted.

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FRICTION

• Friction force that opposes the motion of
  objects that are touching
• Static
• Sliding
• Rolling
• Fluid

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GRAVITY

• Gravity force that attracts or pulls objects
  together
• Acts downwards toward center of Earth
• Causes objects to accelerate as they fall

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Newtons Laws

• 1st - An object at rest remains at rest OR an
  object in motion remains in motion,unless acted
  on by an outside force

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Newtons Laws

• 1st law Law of inertia.
• Inertia- tendency of object to resist change in
  motion.
• Think seat belts, airbags, etc.

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Newtons Laws

• 2nd acceleration of an object depends on the
  force on the object and the mass of the object
• F (m)(a) OR a f / m

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PRACTICE

• F (m)(a)
• How much force is required to move a car with a
  mass of 1200 kg at a rate of 3.0 m/s2?
• What is the force on a 80 kg box accelerating
  down a ramp at 2 m/s2?

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Newtons Laws

• Mass measure of inertia, amount of matter in an
  object
• Weight- force of gravity on an object

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• This formula is a substitute for F (m)(a)
• g 9.8 m/s2 (on earth)
• Units for weight newtons (N)

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Newtons Laws

• 3rd for every action or force, there is an
  equal and opposite reaction or force
• Bumper cars
• If the forces both act on the same object the
  object will not move (net force 0)

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MOMENTUM

• Momentum units are kgm/s
• No velocity? no momentum!
• Describes how mass and velocity are effected by
  each other.

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• Conservation of momentum-
• The loss of momentum in an object is the gain of
  momentum in another object