Mechanics definitions Flashcards
speed
rate of change of distance
velocity
rate of change of displacement
displacement
vector measurement of distance in a certain direction
Vector
A quantity with magnitude and direction
Scalar
A quantity with magnitude only
Average speed
Total distance / total time taken
Instantaneous speed
The speed at any particular time on a journey
Acceleration
The rate of change of velocity
Displacement-time graph
A graph showing the positions visited on a journey (displacement on the y-axis and time on the x-axis)
Velocity-time graph
A graph showing the velocities on a journey (velocity on the y-axis and time on the x-axis)
Resultant force
The total force acting on a body when all the forces acting are added together accounting for their directions
Free-body force diagram
A diagram where all the forces acting are drawn on at the points where they act
Equilibrium
A body is in equilibrium if there is zero resultant force and zero resultant moment
Principle of moments
body will be in equilibrium if the sum of the clockwise moments acting on it is equal to the sum of the anticlockwise moments
Centre of gravity
The point through which the weight of an object appears to act
Newton’s first law of motion
An object will remain at rest, or in a state of uniform motion, until acted on by a resultant force
Newton’s second law of motion
an objects mass is constant the resultant force needed to cause an acceleration is given by: F = ma
Newton’s third law of motion
For every action there is an equal and opposite reaction
Kinematics
The study of the description of motion of objects
Uniform motion
Motion when there is no acceleration
Resolving a vector
Determination of a pair of vectors at right angles to each other
Projectile
A moving object on which the only force acting is gravity
Component
A part of a vector quantity in a certain direction (usually horizontal or vertical).
