Mechanics Flashcards
Scalar
A quantity which has magnitude only
Vector
A quantity which has magnitude and direction
Displacement
The separation between two points in a given direction
Distance
A measure of the separation between two points
Speed
The distance travelled per unit of time
Velocity
The rate of change of displacement
Acceleration
The rate of change of velocity in respect to time
The principle of conservation of momentum
In a closed system, momentum before= momentum after
Force
That which changes or tends to change the velocity of an object
Weight
The force with which a mass is attracted to a planet
Friction
The force that opposes motion between two surfaces in contact
Newton’s first law of motion
A body remains at rest or in uniform motion unless acted on by a resultant
Newton’s second law of motion (words)
The rate of change of momentum is directly proportional to the applied force and takes place in the same direction in which the force acts
Newton’s third law of motion
For every action there is an equal and opposite reaction
Lever
Any rigid body that can rotate about a fixed point called a fulcrum
The centre of gravity
The point through which the weight of an object appears to act
Conditions for equilibrium
- The forces up= the forces down
2. The sum of the moments about any point must be zero
A Couple
Two equal parallel forces that act in opposite directions.
Archimedes’ principle
The upthrust= the weight of fluid displaced
Law of floatation
A floating body displaces its own weight of fluid
Boyle’s law
For a fixed mass of gas at constant temperature, its volume is inversely proportional to its pressure
The moment of a force/couple
M/T=Fd
F= force
d= distance
T= torque (couple)
Friction
The force that opposes motion between two surfaces in contact
Energy
The ability to do work
Joule
The work done when 1N displaces an object by 1m
Watt
W=J/s
The efficiency of a machine
The energy output as a percentage of energy input
Simple harmonic motion
Motion where an objects acceleration is directly proportional to its displacement from a mean position and always directed towards it
Periodic time
The time taken to complete one revolution
Equation for periodic time
T= 2pieR/v
Mass
The measurement of how difficult it is to accelerate a body
Newtons second law of motion (equation deriving)
F= Mv-Mu/ T
