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45 Cards in this Set
- Front
- Back
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Recognize that an object moving with a constant speed is represented by a
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linear “position vs time” graph
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Units For Displacement
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Ex.- 4 ft. to the East
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Units For Distance
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feet
inches cm m |
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Units For Speed
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Ex.- 2 ft/sec.
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Units For Velocity
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Ex.- 1 ft./sec. to the East
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How To Calculate Average Speed
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distance traveled divided by total time
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How To Calculate Average Velocity
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displacement divided by total time
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Positive Velocity
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movement in the positive direction
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Negative Velocity
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movement in the negative direction
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Distance vs. Displacement
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Distance- length
Displacement- the change in position of an object |
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Speed vs. Velocity
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Speed- the magnitude of velocity
Velocity- the rate of change of position |
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* Important Info *
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Average speed and average velocity are
generally not equivalent because total distance and total displacement are generally not the same. |
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If an object increases its speed while traveling in the negative direction,
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its velocity actually decreases
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If an object decreases its speed while traveling in the negative direction,
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its velocity actually increases.
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As a rule, if the object’s velocity and acceleration
are in the same direction (have the same sign), |
we can say that the object’s speed is increasing.
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If the velocity and acceleration are in opposite
directions (have opposite signs), |
we know
that the object’s speed is decreasing. |
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Position-Time Graphs
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the slope of a position-time graph at any instant is the instantaneous velocity of the object
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Position-Time Graphs
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horizontal graph segments indicate that the object is “at rest”
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Position-Time Graphs
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graph segments moving upward imply movement in the positive
direction |
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Position-Time Graphs
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graph segments moving downward imply movement in the negative direction
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Position-Time Graphs
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straight line graph segments indicate constant speed
curving graph segments indicate changing speed |
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Position-Time Graphs
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graph segments becoming steeper indicate an increase in speed
graph segments becoming less steep indicate a decrease in speed |
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Velocity-Time Graphs
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the slope of a velocity-time graph is the acceleration of the object
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Velocity-Time Graphs
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horizontal graph segments indicate that the object has constant velocity
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Velocity-Time Graphs
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graph segments above the x-axis imply movement in the positive
direction graph segments below the x-axis imply movement in the negative direction |
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Velocity-Time Graphs
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horizontal segments on the x-axis indicate no movement
straight line graph segments indicate constant acceleration graph segments moving upward indicate an increase in velocity graph segments moving downward indicate a decrease in velocity |
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Velocity-Time Graphs
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a change of direction is indicated whenever the graph crosses the x-axis
an increase in speed is indicated by graph segments moving away from the x-axis |
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Acceleration-Time Graphs
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horizontal graph segments indicate that the object has constant acceleration
a horizontal graph segment on the x-axis indicates that the object has constant velocity (no acceleration) |
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Acceleration-Time Graphs
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graph segments above the x-axis imply increasing velocities
graph segments below the x-axis imply decreasing velocities |
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How To Determine Acceleration
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change in velocity divided by change in time
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* Important Concept *
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use the quadratic relationship between distance and time for accelerating objects to determine distances an accelerating object travels in specified times
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recognize that an accelerating object is represented by
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a curving “position vs time” graph
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Positive vs. Negative Accelerations
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When an object is speeding up, the acceleration is in the same direction as the velocity. Thus, this object has a positive acceleration
when an object is slowing down, the acceleration is in the opposite direction as the velocity. Thus, this object has a negative acceleration |
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Free-Falling Objects
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do not encounter air resistance
All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s (often approximated as 10 m/s/s for back-of-the-envelope calculations) |
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How mass affects the period of an oscillating spring
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The larger the mass, the longer it takes for the period to be completed
larger mass = longer period |
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How mass affects the period of simple pendulum
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has no affect
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How length affects the period of a simple pedulum
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The period of a simple pendulum is directly proportional to the length squared
The period increases (doubles) as the length increases |
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Newton's 3rd Law of Motion
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For every action, there is an equal and opposite reaction
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Inertia
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“the tendency of an object to resist any change in its motion.”
The more inertia an object has, the more difficult it is to change its motion. |
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Mass
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a quantitative (numerical) measure of inertia
The more mass an object has, the greater its resistance to changing its motion. |
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Force
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a push or pull
Force= mass x acceleration |
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Weight
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a measure of the gravitational force
that a massive object, such as a star or planet, puts on another mass Weight= mass x 9.8 |
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Newton's 1st Law of Motion
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An object at rest remains at rest and an object in motion continues in motion in a straight line at a constant speed unless acted on by a nonzero net force
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Newton's 2nd Law of Motion
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A net force causes an object to accelerate in the direction of the net force. The acceleration is directly proportional to the net force and inversely proportional to the object's mass
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Newton's 3rd Law pairs of forces:
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never cancel each other out
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