Mechanics Flashcards
Scalar Quantity
Quantity with magnitude only, no directional component.
eg: time.
Vector Quantity
Quantity with both magnitude and direction.
eg: velocity.
Momentum
(p), is the product of mass and velocity.
Principle of Conservation of Momentum
The total momentum before an interaction is equal to the total momentum after, provided no resultant force acts on the system.
Force
(F), is that what causes acceleration.
Newton’s First Law of Motion
A body will remain at rest or continue moving at a constant velocity unless acted upon by an unbalancing external force.
Newton’s Second Law of Motion
The rate of change of momentum is proportional to the applied force and takes place in the direction of the force.
Newton’s Third Law of Motion
For every action there is an equal and opposite reaction, action and reaction do not happen on the same body.
Newton’s Law of Universal Gravitation
The force of attraction between two point masses is proportional to the product of their masses and inversely proportional to the square of the distance between them.
Acceleration due to Gravity
The acceleration experienced by a body in free fall within the gravitational field of a massive body.
Weight
The force equal to the product of mass and acceleration due to the gravity.
Centre of Gravity
A point at which the whole weight of a body appears to act.
Normal Reaction
A reactionary force which is perpendicular to that surface and is due to the weight of the object.
Moment of Force
The force multiplied by the perpendicular distance to the fulcrum.
The fulcrum is a fixed point about which a rigid body (called a level) is free to rotate.
Moment
The turning effect of a force / (N m)
Lever
A rigid body that is free to rotate about a fixed axis.
Couples
A pair of equal and opposite forces whose lines of action do not coincide.
Torque
The torque of a couple (T) is equal to the magnitude of one of the forces multiplied by the distance between them.
(T=Fd)
Conditions for Equilibrium
Law 1: The vector sum of the forces in any direction is zero.
(Forces up = Forces down, Forces left = Forces right)
Law 2: The vector sum of the moments about any point is zero.
(Σ Clockwise moments = Σ Anticlockwise moments)
Density
mass per unit volume. (kg m^-3)
Pressure
force per unit area. (Pa)
Archimedes Principle
When a body is wholly or partially submerged in a fluid, it experiences an upthrust equal to the weight of the fluid displaced.
Law of Flotation
The weight of a floating body is equal to the weight if the fluid it displaces.
Bouyancy
The upward force on a body that is wholly or partially immersed in a fluid.
Boyle’s Law
Pressure is inversely proportional to volume for a fixed mass of gas at constant pressure.
Work
The product of force and displacement.
Kinetic energy
The energy a body has due to its motion.
Potential Energy
The energy a body has due to its position or condition.
Principle of Conservation of Energy
Energy can niether be created or destroyed; it merely changes from one form to another.
Power
(P), the rate at which work is done.
Angular Velocity
(ω), the rate of change of angle
Linear Velocity
(v), the speed of a particle in a direction perpendicular to the radius at that point.
Periodic Time
(T), the time taken to do one complete revolution, cycle or oscillation.
Centripital Acceleration
The acceleration of an object travelling in uniform circular motion; it is directed toward the centre of the circle.
Centripital Force
The force required to maintain uniform circular motion; it is directed towards the centre of the circle.
Kepler’s Third Law
The sqaure of the periodic time of a satellite’s orbit around a planet is proportional to the cube of the radius of the orbit (including the radius of the planet) and inversely proportional to the mass of the planet.
Hooke’s Law
When an object is stretched, bent or deformed the restoring force (F) is proportional to the displacement (s) from its equilibrium position.
Elastic Constant
(k), is the consant of proportionality between the applied force and the resulting displacement of a given spring.
Elasticity
The ability of a body to resist a distorting influence or stress and to return to its original size and shape when the stress is removed.
Simple Harmonic Motion
(SHM), is where the acceleration (a) of a body towards a particular point is proportional to its displacement (s) from that point.
Amplitude
(A), the maximum distance that an object moves from its equilibrium position
Frequency
(f), the number of cycles (or oscillations) the object completes per unit time.
Period
(T) of a particle excecuting SHM is the time taken for one complete oscillation.
