Chapter 1 : Kinematics - Describing Motion Flashcards
Definitions and key elements
Two important things to consider when approaching kinematics :
- Motion of bodies in a straight line
2. Only consider uniform acceleration ( so acceleration that is constant and does change)
Definition of displacement
°distance travelled by a body, in a particular/specified direction
°shortest straight line distance between two points
°is the distance of an object from a fixed reference point in a specified direction
Unit : m
Definition of distance
°actual length of a path followed by a body
Unit : m
Definition of distance
°actual length of a path followed by a body
Unit : m
Definition of Speed
° rate of change of distance
° distance travelled per unit time
Unit: ms-1
Definition of velocity
° rate of change of displacement
° distance covered by a body in a specified direction (or displacement) per unit time
Unit: ms-1
Definition of acceleration
°rate of change of velocity
Unit: ms-2
Displacement - time ⌚ graphs :
What is the gradient equal to?
Velocity
If the gradient of a displacement - time ⌚ graph is a straight line between the displacement and time the velocity is
Constant
The steeper the slope of a displacement–time ⌚ graph the…
Greater the velocity
If the slope of a displacement - time ⌚ graph is zero that means 2 things :
- Displacement is not changing
- Velocity =0
Therefore the object is not moving
If the slope of a displacement - time ⌚ graph suddenly becomes negative it means…
The direction of the object is changing. The object is moving back the way it came
If the displacement - time ⌚ graph is curved that means
The velocity is changing and is not constant
Definition of vector addition :
°combining 2 or more vector quantities through addition to determine the resultant (the combine effect) of the vectors
Definition of a scalar quantity :
A quantity that only has magnitude
Definition of a vector quantity :
A quantity that has both magnitude and direction (direction is shown by signs +/- or arrows)
All forms of energy (including work done) are scalar/vector quantities?
Scalar
Give 7 examples of scalar quantities :
- mass ⚖
- time ⌚
- Temperature 🤒🌡️
- Distance 🛣️
- Resistance
- pressure
- speed 🛑
7 examples of vector quantities :
- Weight kg
- acceleration
- velocity
- displacement
- Force
- Momentum
- Torque
Definition of instantaneous speed :
°the speed of an object measured over a short period of time
Definition of instantaneous speed :
°the speed of an object measured over a short period of time
NB to know the formula for a trapezium when working the area under a graph.
What is the formula?
How can you derive s=((u+v) /2)x t from it
Area of a trapezium =h/2.(a+b)
°a and b are the heights of the trapezium and h is the base
Think of an v-t graph with a trapezium shaped area….
h= the base which is time ⌚
a= initial velocity u
b= final velocity v
Therefore: t/2.(u +v)
Which is the same as s=((u+v) /2)x t
Resolving a vector refers to…?
Splitting a vector which is at an angle to the horizontal into 2 components
