Download Chapter 2 Motion

Chapter 2 Motion
I.
Describing Motion
Motion
1. Motion and Position
a. You do not need to see something move
to know that it has moved.
b. Reference point is needed to determine
position of an object.
c. Motion occurs when object changes its
position relative to a reference point.
2. Frame of Reference
d. Coordinate system in which position of
the object is measured
3. Distance
a. Distance – how far an object has
moved.
b. Measured in meters.
4. Displacement
a. Distance and direction of an objects
change in position from the starting
point. Think absolute value!
Speed
a. Speed- distance an object travels per unit of time.
1. Calculating Speed
a. Change over time is called rate
b. Speed = distance ÷ time
c. SI unit for distance is meter and unit for time is
second so speed is measured in meters per
second.
2. Motion with Constant Speed
a. If you are traveling at a constant speed you can
measure speed over any distance interval.
3. Changing Speed
a. Speed is not usually constant
4. Average Speed
a. Total distance traveled divided by total time of
travel
5. Instantaneous Speed
a. Speed at any given point in time.
6. Changing Instantaneous Speed
a. When something is speeding up or slowing
down instantaneous speed is changing.
C. Graphing Motion
a. Motion of object over a period of time can be shown
on distance-time graph
b. Time = horizontal axis
c. Distance =vertical axis
d. Constant speed will result in straight line
e. Steepness of a line is the slope (think skiing) on this
graph the slope = the speed
1. Changing speed
a. Straight line constant; moving line = changing
speed
2. Plotting a distance-time graph
a. Each axis must have a scale that can cover the
range of numbers to be plotted
b. Choose equal intervals
Velocity
a. Speed describes only how fast something is moving
b. Velocity – describes speed AND direction
c. Velocity of an object can change even if the speed
remains the same. Can I get a volunteer??
Motion of the Earth’s Crust
Moving Continents
a. Plates move so slowly their movements
measured in centimeters per year. What kind
of unit is this???
Section Review – vocab self-check ?s 2 and 4
II. Acceleration
A. Acceleration, Speed, and Velocity
a. Acceleration is the rate of change in velocity
NOT just speed.
b. Acceleration occurs when an object changes its
speed, its direction, or both.
1. Speeding Up and Slowing Down
a. An object that is slowing down is also
accelerating!
b. Acceleration is about speed AND direction.
2. Changing direction
a. Anytime an object changes its direction its
velocity AND acceleration change
B. Calculating Acceleration
a. Acceleration is the rate of change in velocity
b. To calculate figure out change in velocity divided
by the time.
i. To calculate the change in velocity subtract
the initial velocity from the final velocity.
c. Acceleration = If my final velocity is greater than
my initial velocity my acceleration is positive,
meaning I am speeding up
d. Measured in m/s squared.
C. Calculating Positive Acceleration
a. If something is speeding up the final speed is
greater than the initial speed and acceleration is
positive
D.Calculating Negative Acceleration
a. If something is slowing down the final speed is
less than the initial speed and the acceleration is
negative.
Section review – vocab questions 1 and 3
III Motion and Forces
A. What is Force?
a. A push or a pull
b. Sometimes you cannot feel a force being
exerted
1. Changing Motion
a. Force can cause the motion of an object to
change
2. Balanced Forces
a. Force does not always change velocity
b. 2 or more forces act on an object at the same
time it is called net force. Think tug of war!
c. Forces on an object that are equal in size and
opposite in direction are called balanced forces.
3. Unbalanced Forces
a. Unequal forces in opposite directions creates a
net force in the direction of the larger force.
B. Inertia and Mass
a. Inertia the tendency of an object to resist any
change in its motion.
b. An object will keep moving and the same speed
and in the same direction unless an unbalanced
force acts upon it.
c. Inertia is related to mass. Greater its mass
greater its inertia.
1. Newton’s Laws of Motion
2. Newtons First Law of Motion
a. An object moving at a constant velocity keeps
moving at that velocity unless an unbalanced
net force acts on it.
b. If an object is at rest it will stay at rest.
c. This is inertia
C. What Happens in a Crash
a. Car stops but body keeps moving at the speed of the car until something stops it.
Science created seat belts, remember safety????
b. Seat belt is loose to it slows you down slower. Minimize force.
c. Air bags provide cushion to minimize force.
Section Review – vocab self-check question 1,2,3