Mechanics Flashcards
Vector
A quantity which has magnitude and direction
Scalar
A quantity which has magnitude only
Distance
A measure of the separation between two points
Displacement
The separation between two points in a given direction
Speed
The distance travelled per unit time
Velocity
The rate of change of the displacement
Acceleration
The rate of change of the velocity
Momentum
The product of the mass and velocity of a body
The principle of conservation of momentum
In any closed system of colliding bodies, the total momentum remains constant
Force
That which can cause acceleration
Newton
A force of one Newton gives a mass of one kg and acceleration of 1 m/s2
Weight
A force equal to the product of mass and acceleration due to gravity
Friction
The force that opposes motion between two surfaces in contact
Newton’s First law of motion
A body remains at rest or a uniform motion unless acted on by a resultant force
Newton’s second law of motion
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
F = ma
Newton’s third law of motion
For every action there is an equal and opposite reaction
Work
Done when a force causes a body to be displaced
W = Fd
Energy
The ability to do work
1 Joule
The work done when a force of 1 N this place is an object by 1 m
The principle of conservation of energy
States that energy can neither be created nor destroyed, but can change from one form to another
Power
The race at which work is done for energy is converted P = W/t
1 Watt
The race of doing work equal to 1 joule per second
Potential energy
The energy a body has due to its position or state
Kinetic energy
The energy a body has due to its motion
Renewable source of energy
One that will not be exhausted e.g. wind tidal and solar. A non-renewable source will eventually run out; coal oil natural gas
Efficiency of machine
Useful energy output as a percentage of energy input
Lever
Any rigid body that is free to rotate about a fixed point called a fulcrum
The centre of gravity
The point of an object through which the weight of the object appears to act
The moment of a force (torque)
The force applied multiplied by the perpendicular distance to the fulcrum M =Fd
Conditions for equilibrium
- The vector sum of the forces in any direction must be zero
- The sum of the moments about any point must be zero
Couple
2 equal parallel forces that act in opposite directions
Moment of a couple
The magnitude of one force multiplied by the perpendicular distance between the two forces
Hooke’s law
In an elastic body the restoring force is proportionately the displacement of the stretched object from its equilibrium position
F = -ks
Simple harmonic motion
The acceleration of a body towards its mean position is directly proportional to its distance from that position and always directed towards it
A = - ω s
Newton’s law of universal gravitation
The force between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distance between the
Centripetal Force
The force required to maintain uniform circular motion. It is directed towards the center of the circle
Centripetal acceleration
The acceleration of an object to traveling in uniforms circular motion. It is directed towards the center of the circle
Angular velocity
The rate of change of an angle
Angle
Measured ingredients is equal to the arc length divided by the radius
Elastic constant
The constant 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
Periodic time
The time taken to complete one revolution
Kepler’s third law
The square of the periodic time of a satellite is directly proportional to the cube of its radius of orbit and inversely proportional to the mass of the planet in orbits
Density
The mass per unit volume of a substance
p=m/V
Pressure
The force per unit area
P = F/A
Archimedes principle
When a body is partially or fully immersed in a fluid, it experiences an uptrust which is equal to the weight of fluid displaced
Law of flotation
A floating body displaces his own ways of fluid
Boyles law
For a fixed mass of gas at constant temperature its volume is inversely proportional to its pressure
Acceleration due to gravity
The acceleration experienced by a body in free fall within the gravitational field of a massive body
