Ch' 2 Linear motion

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Ch. 2 Linear motion Motion is easy to recognize
but hard to describe. Rate is any quantity
divided by time. We can describe motion then as
speed, velocity, and acceleration. Motion along a
straight line is called linear motion.
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Motion is relative. This means that we describe
motion of an object relative to some other
object. Speed is a measure of how fast something
is moving. It is the rate at which a distance is
covered.
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Any combination of distance divided by time
describes speed. Ex miles/hour or
meters/second The speed of an object at a
specific time is called instantaneous
speed. Average speed tells us the speed over a
whole trip. Average speed total distance /
time S d / t
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Velocity is speed in a given direction. Ex A
car travels 60 miles/hr speed A car travels 60
miles/hr north velocity. Motion at constant
velocity means it must be in a straight line.
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• An object can be going at a constant speed, but
  if the direction is changing, so is the velocity.
• In a car, we can change the velocity three ways
• Gas pedal to speed up
• Brake to slow down
• Steering wheel to change direction

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Any time that we change the velocity, we
accelerate. Acceleration change in velocity/
time Or A ?v / t We use the term accelerate to
mean both going faster and slowing down.
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The unit is velocity divided by time so we
get Miles/hr/sec Or Kilometers/hr/sec
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Free fall Gravity causes objects to speed up as
they fall. Without air resistance, all objects
fall at the same rate due to gravity. g 10
m/s2 To find the speed of a falling object at any
height, we use v g x t
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When we throw an object up into the air, its
velocity at the top would be zero. It then speeds
up while it is falling back down. The speed
when it reaches your hand is the same as when you
first threw it. To calculate the distance that
something falls, we use d ½gt2