Definitions Flashcards
Scalar
Quantity defined by a magnitude and unit
Vector
Quantity defined by magnitude, unit and direction
Moment
Product of force and its perpendicular distance to a pivot
Centre of mass / gravity
The point where the entire mass / gravity of an object seems to act
Principle of moments
For a system in rotational equilibrium, the summation of the clockwise moments about a point is equal to the summation of the anticlockwise moments about the same point
Velocity
Rate of change of displacement
Acceleration
Rate of change of velocity
Projectile motion
Uniform velocity in one direction and uniform acceleration in a perpendicular direction
Newton’s 1st law
A body will continue in a state of rest or constant velocity unless acted on by a resultant force
Newton’s 2nd law
A body subject to a resultant force will accelerate in the same direction as the resultant force
Fr = ma
Acceleration is directly proportional to fr but inversely proportional to m
Newton’s 3rd law
If body A exerts a force on body B, body B will exert a force that is equal in magnitude but in the opposite direction to body A
Momentum
Product of a body’s mass and velocity
p = mv
Principle of conservation of linear momentum
For a closed system, the total momentum before a collision = total momentum after the collision.
Elastic collision
Ke is conserved, total energy is constant
Inelastic collision
Ke isn’t conserved, total energy is constant
Totally inelastic collisions
2 objects stick together with a large loss in ke, total energy is constant
Impulse
Product of force and time the force is applied for.
f x t
Newton’s 2nd law in terms of momentum
Rate of change of momentum of a body is proportional to the applied force and acts in the same direction as the force
Electric current
Rate of flow of charge
What is Potential difference across a component defined as
Amount of electrical energy transferred to other forms when unit charge passes through the component
Electromotive force
Amount of electrical energy produced from other forms when unit charge passes through a power source
Volt
1 joule of energy dissipated /unit charge
4 conditions required for a couple
Forces are…
Acting in opposite directions
Aren’t along the same straight line
Same size
Parallel
Resistivity
The resistance of 1m of material of cross sectional area m^2
Superconductor
A material which loses all its electrical resistivity to become a perfect conductor when it is below its critical (or transition) temperature
Ohm’s law
Potential difference is directly proportional to the current through it, provided the temperature remains constant
Lost volts
The energy dissipated per unit charge within a cell/power source due to its internal resistance
Work done
Product of force and distance moved in the direction of the force
Potential energy
Stored energy (GPE)
Kinetic energy
Movement energy
Displacement
Change in position of object
Average velocity
Change in displacement divided by time taken
Potential divider (what it does and some real world examples)
Provides variable supply of pd to a circut with a fixed power supply
Lighting /Heating circuits
Kirchhoff’s law
Charge entering a junction = charge leaving junction
