Kinematics Unit 1 Test Flashcards
Average Speed
the total distance covered divided by the total time taken (instant in time)
Average Speed Formula
Vave =
d
–
t
Average Velocity
the total displacement divided by the time interval
Formula For AVERAGE VELOCITY:
average velocity =
displacement
———————
time taken
any “d” is the y-coordinate of a point from the beginning or end of a line
Vave = d2 - d1 ---------- t2 - t1 = ∆d ---- ∆t
Displacement
the change in position from a reference point
- vector quantity
- ->includes magnitude and direction
Displacement Formula
∆d = d2 -d1
When would you use the subtracting displacement formula?
∆d = d2 - d1
When there is 1 displacement or when vectors follow the same direction
EX. both vectors are going [E]
———————>——–>
When would you use the adding displacement formula?
∆d = ∆d1 + ∆d2
When there is more than 1 displacement or when vectors are in different directions
Ex one vector going [W] then another traveling [E] from that last point
Distance
the length of a path taken
- a scalar quantity
- ->includes magnitude only
Instantaneous Velocity
the moment-to-moment measurement of an object’s velocity
if the velocity of an object is CONSTANT…
then the instantaneous velocity is equal to its average velocity & equal to the SLOPE OF THE LINE on a p-t graph
if the velocity CHANGES every moment during the motion of an object…
then no portion of the p-t graph is a straight line
–>p-t is made up of tangents
How can you determine the slope of a curve?
each tangent on a curve has a unique slope, which represents the velocity at that instant
What does the slope of a straight line of a p-t graph give?
What does the slope of a tangent at a point on a curved p-t graph give?
straight line: the velocity
tangent: the instantaneous velocity
Magnitude
the number and unit of a vector
Non-Uniform Motion
an object that moves through unequal displacements in equal intervals of time
Origin
a main reference point
Position
the location of an object relative to a reference point
- vector quantity
- ->includes magnitude, direction and a reference point
Characteristics and Examples of Scalar Quantities
-only have a size and unit
2 Parts:
- Number
- Unit
Examples:
Distance (d) - 5m
Speed (v) - 15km/hr
Time (t) -8.0s
Characteristics and Examples of Vector Quantities
-have a size, unit AND direction
3 Parts:
- Number
- Unit
- Direction
Examples:
Displacement (∆d) - 5m [E]
Velocity (v) - 15km/hr [NW]
Acceleration (a) - 8m/s [FORWARD]
What are the 3 ways motion can be described by?
- A reference point
- A magnitude (number and unit)
- A direction
as well as certain physical characteristics such as SPEED, DISTANCE, TIME, VELOCITY, ACCELERATION etc
Speed
the distance covered per unit time
- scalar quantity
- ->SI unit is m/s or km/h
Tangent
a straight line that touches a curve only at one point
Uniform Motion
motion with no change in direction
Velocity
displacement per unit time
To Calculate Velocity:
look at the slope of a position-time graph for an object in uniform motion
slope =
y2 - y1
———–
x2 - x1
Conversion to get a smaller answer:
m —> km
x and y equal whatever unit of measure the question pertains to
(1/x) multiplied by (1/y)
Conversion to get a larger answer:
km —> m
x and y equal whatever unit of measure the question pertains to
(x/1) multiplied by (y/1)
When are the distance and the magnitude of displacement equal, and when are they different?
If the object does not change direction, then the distance and displacement are equal. If the object does changes direction, then the distance and displacement are different.
What is the difference between speed and velocity?
Speed is distance covered per unit time and is a scalar quantity.
Velocity is displacement per unit time and is a vector quantity.
Describe the relationship between the velocity and acceleration vectors when an object speeds up. How does this relationship change when the object slows down?
When the object is speeding up, the velocity and acceleration vectors have the same sign. They have different signs when the object is slowing down.
Positive diagonal line on a POSITION-TIME graph means?
slope is positive:
-velocity is constant and positive
Negative diagonal line on a POSITION-TIME graph means?
slope is negative:
-velocity is constant and negative
Curved slope on a POSITION-TIME graph means?
-velocity is not constant as the object is undergoing acceleration
Horizontal line on a POSITION-TIME graph means?
the object is stationary as the position does not change with time
Positive diagonal line on a VELOCITY-TIME graph, in the POSITIVE QUADRANT means?
object is speeding up
- positive velocity
- positive acceleration
Positive diagonal line on a VELOCITY-TIME graph, in the NEGATIVE QUADRANT means?
object is slowing down
- negative velocity
- positive acceleration
Negative diagonal line on a VELOCITY-TIME graph, in the POSITIVE QUADRANT means?
object is slowing down (in the negative direction)
- positive velocity
- negative acceleration
Negative diagonal line on a VELOCITY-TIME graph, in the NEGATIVE QUADRANT means?
object is speeding up (in the negative direction)
- negative velocity
- negative acceleration
Horizontal line on a VELOCITY-TIME graph means?
the object is moving at a constant velocity
- positive or negative velocity (depending on which quadrant the line is in)
- zero acceleration
Horizontal line on the X-AXIS on a VELOCITY-TIME graph means?
object isn’t moving
-velocity is zero
V-T GRAPH: What happens if a line crosses over the x-axis from the positive region to the negative region of the graph (or vice versa)?
the object has changed directions
V-T GRAPH: how can you tell if an object is speeding up?
the magnitude of the velocity is increasing
V-T GRAPH: how can you tell if an object is slowing down?
the magnitude of the velocity is decreasing
Acceleration
rate of change of velocity per unit time
An object undergoes acceleration if…
the MAGNITUDE of it’s velocity changes, while its direction remains the same
the DIRECTION of it’s velocity changes, while its magnitude remains the same
there is a change in the magnitude AND direction
Acceleration Formula
a =
∆v
—-
∆t
∆t
Converting a P-T graph to a V-T graph:
SLOPE; HORIZONTAL LINE
Which is also the same as converting a V-T to an A-T
- mark each point on the P-T graph where the slope of the graph changes
- determine the SLOPE (velocity) of each line segment
- draw a horizontal line on the appropriate y-axis for the value of the slope, aligning the x-values to match the moments in time (s) where the velocity changes on both the P-T and V-T graph
- wherever there is a horizontal line on the P-T, a corresponding horizontal line is drawn right on the x-axis of the V-T to show 0 velocity
Converting a V-T graph into a P-T graph:
AREA; DIFFERENT LINE SEGMENTS
- divide the area under the V-T graph into a series of sections with defined areas (triangles and rectangles
- calculate the AREA (displacement) of each section of the V-T graph, noting in particular whether it is positive or negative
- start off by plotting the first point (value of area1) from the V-T onto the P-T and then add the value of area2 to the value of area1 to find the next point on the P-T. Continue to do this for every point you need to plot
- wherever there are horizontal lines on the V-T graph, use a ruler to draw straight lines on the P-T where the constant motion takes place (match the moments in time (s) on both graphs)
- connect the remaining dots (without a ruler)
- wherever there is a horizontal line on the x-axis of a V-T, a corresponding horizontal line is drawn the P-T to show 0 displacement
