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Conceptual Physics - Chapter 4:Linear Motion
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Study set of questions from Chapter 4 of Conceptual Phyics by Hewitt
Terms in this set (26)
Relative
Describes the motion on one object with respect to another
An object is moving if
It's position relative to a fixed point is changing.
Speed Equation
distance ÷ time
Units of Speed
m/s, km/h, mi/h, cm/h light years/century
Average Speed Equation
Total distance covered ÷ Time Interval
Instantaneous Speed
The speed at any instant
Describe how you would calculate speed
Divide the distance covered by the time it takes
Velocity
speed in a given direction
Constant velocity
motion in a straight line at constant speed
Changing velocity
change in either the speed or the direction or both
How is velocity different than speed?
Speed is a description of how fast an object moves; velocity is how fast and in what direction.
Acceleration
Change of velocity ÷ Time Interval
Deceleration
decreases in speed
Change in direction
Results in a form of acceleration because the motion is no longer constant (direction has changed).
Change in speed (along a straight line)
Results in an acceleration defined by (change in speed) ÷ time interval
What is the relationship between velocity and acceleration?
Acceleration is the rate at which velocity changes.
How do you calculate acceleration?
Divide the change in velocity by time
Free fall
An object moving under the influence of gravitational force only
Elapsed time
The time that has elapsed since the beginning of any motion.
Equation for the instantaneous speed ν of an object falling from rest
ν=gt where g is acceleration due to gravity and t is the elapsed time from the resting position
Equation for the instantaneous speed of an object thrown straight up in the air (rising objects)
ν= ν₁-gt where ν₁ is the initial upward velocity, g is acceleration due to gravity and t is the elapsed time from the beginning of the throw
Equation for the distance an object travels in free fall from rest
d=½gt² where g is acceleration due to gravity and t is elapsed time from the resting position
Acceleration of an object in free fall on Earth
∼10 m/s² (or more closely 9.8 m/s²)
What does the speed versus time graph look like for a free falling object?
It is a straight line or linear because the acceleration is constant. The slope of the line represents the acceleration due to gravity.
What does the distance versus time graph look like for a free falling object?
It is parabolic or nonlinear because the speed is increasing at the rate of the square of time elapsed (it is exponential). The slope of the line at a particular point represents the speed at that particular instant in time.
How does air resistance affect falling objects?
Air resistance noticeably slows the motion of things with large surface areas like falling feathers or pieces of paper. But air resistance less noticeably affects the motion of more compact objects like stones and baseballs.
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