Kinematics Flashcards
(31 cards)
Displacement
A vector quantity, referring to the distance from an object’s initial position to its final position, including direction. Expressed as a vector.
s = final position - initial position
Velocity
A measure of how fast an object moves through a displacement. Vector, as it has direction.
v (arrow) = displacement/time
Acceleration
Change in velocity. Vector.
Distance
A scalar quantity referring to the total length of an object’s path, regardless of direction.
Speed
The rate at which an object moves. Scalar, as it has no direction.
v = distance / time
Uniform motion
Motion with no acceleration in one direction. The displacement per second is constant.
On a d-t graph, this is a straight diagonal line. On a v-t graph, this is a horizontal line. On an a-t graph, this is a horizontal line at zero.
One-dimensional motion
Motion that happens in a single straight line along the x or y axis.
walking 10m east
Two-dimensional motion
Motion that happens in two directions, i.e. along the x and y axes.
walking 10m east, 5m north
Uniform accelerated motion
Motion with constant acceleration in one direction.
On a d-t graph, this is an exponential curve. On a v-t graph, this is a straight diagonal line. On an a-t graph, this is a horizontal line.
Projectile motion
Remember to distinguish between horizontal and vertical velocity.
Motion in two directions (two-dimensional).
On a d-t graph, this is generally a parabola (starting from rest).
Horizontally, uniform motion is experienced. Vertically, uniform accelerated motion is experienced (downward).
Uniform circular motion
Also known as cetripetal motion.
Motion that occurs in two directions (as circles are two-dimensional), in a circle.
Relative motion
Motion described from different frames of reference in two directions (two-dimensional). By default, the Earth or stationary objects on Earth are the frame of reference.
Formula for uniform circular motion, given period?
acceleration = 4 * pi^2 * radius / period^2
Formula for uniform circular motion, given frequency?
acceleration = 4 * pi^2 * radius * frequency^2
Relationship between frequency and period?
They are inverses (1/frequency = period).
What is the acceleration direction of an object taking a circular path?
It is always pointed towards the centre of the circular path, i.e. centripetal.
Period
The time taken to go around a circle once. Represented as uppercase T.
Frequency
The number of times the object circles in one second (hertz).
Vector
A physical quantity with magnitude and direction.
e.g. 45 km [E]
Scalar
A physical quantity with magnitude but no direction.
e.g. 45 km
Instantaneous velocity
The velocity of the object at one specific point in time. Derived by finding a slope tangent to the point.
The slope and y-intercept on a position-time graph represent:
Slope: velocity (the steeper, the higher the velocity)
A negative slope indicates a change in direction.
Y-intercept: starting position
The slope and y-intercept on a velocity-time graph represent:
Slope: Acceleration
A negative slope indicates a decrease in speed in the positive direction. The object is still moving in the positive direction.
Y-intercept: Initial velocity
The slope and y-intercept on an acceleration-time graph represent:
Slope: Rate of change in acceleration
Y-intercept: Starting acceleration
