Displacement and Position-Time Graphs Test Flashcards
Mechanics
the study of motion
Kinematics
the science describing the motion of objects using words, diagrams, numbers, graphs and equations
What does kinematics allow us to do?
ultimately develop sophisticated mental models that serve to describe and ultimately explain the motion of real world objects
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
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]
Position
the location of an object relative to a reference point (a vector quantity)
—> includes magnitude, direction, and a reference point
EX. 15m [N] of the school
Displacement
the change in position from a reference point (a vector quantity)
—> includes magnitude, and direction
EX. 15m [N] of some starting point
Displacement Formula
∆d = d2 - d1
Change in:
Vector:
Final position:
Initial position:
∆
d
d2
d1
When would you use the subtracting displacement formula?
∆d = d2 - d1
when there is 1 displacement
(when the 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
(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 (scalar quantity)
—> includes magnitude only
EX. 15 km
Positive Sign Conventions
East [E]
Right [R]
North [N]
Up
Negative Sign Conventions
West [W]
Left [L]
South [S]
Down
Vector Drawing Rules
- The vector is drawn pointing in the direction of the vector
- ———> 10km [E] - The length is proportional to the magnitude of the measurement
(20km is 2x longer than 10km so the vector should be too)
———-> 10km/hr 20km/hr
Colinear Vectors
vectors that lie along the same line
- only colinear vectors add or subtract like ordinary numbers or scalars
- vectors are also colinear if they lie along a straight line in opposite directions
Position-Time Graphs
a position-time graph gives a visual representation of the motion of an object
Uniform Motion
motion with no change in direction
Straight Line on a position-time graph means?
an object is moving through equal displacement in equal time intervals (constant rate)
Horizontal Line on a position-time graph means?
the object is stationary as the position does not change with time
Velocity
the change in distance per time unit
EX. m/s or km/hr
To Calculate Velocity:
look at the slope of a position-time graph for an object in uniform motion
slope =
y2 - y1
———–
x2 - x1
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 =
df - di
——–
tf - ti
∆t
velocity can be positive or negative
—> moving in the positive or negative direction
in other words, the objects movement can be towards or away from the origin
Average Velocity Between 2 Points:
the average velocity between any 2 points on a position time graph is equal to the slope of the line drawn between the 2 points
Significant Digit Rules For Adding & Subtracting
round the sum or difference so that it has the same number of decimals places as the measurement HAVING THE FEWEST DECIMAL PLACES
Significant Digit Rules For Multiplying & Dividing
express the product or quotient to the same number of significant digits as the multiplied or divided number HAVING THE LEAST NUMBER OF SIGNIFICANT DIGITS
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)
