PH1.1

VECTORS contain magnitude and direction.

i.e momentum, acceleration, velocity, weight, force 

SCALARS contain magnitude only. 

i.e. time, density, speed, distance, energy. pressure

"If object A exerts a force on object B, then object B exerts an equal but opposite force on object A."

A moment is a turning effect of a force. 

It can also be called a torque.

Moment = force X perpendicular distance from pivot

    (Nm)       (N)                           (m)

For a body to be in equilibrium:

• Sum of the clockwise  = Sum of anticlockwise             moments                 moments 

For an object to be in equilibrium:

• NO NET FORCE ACTING IN ANY DIRECTION
• NO NET TURNING EFFECT ABOUT ANY POINT

Centre of Gravity of an object is the point at which we can take its entire weight to act. 

Centre of Mass of an object is the point at which we can takes its entire mass to act. 

When an object is outside the base it will topple.

The displacement of point B from point A is the shortest distance from A to B, together with the distance.

Mean Speed: total distance travelled / total time taken 

Instantaneous Speed: rate of change of distance

Mean velocity: total distance/ total time taken 

Instantaneous Velocity = rate of change of displacement 

Mean Acceleration = change in velocity / time      taken 

Instantaneous Acceleration =  rate of change of velocity 

Terminal velocity occurs when the frictional force = driving force.

The driving force must be constant and the frictional force must increase with speed.

Graphs of terminal velocity 

Work done = Force x Distance moved in direction of force

Work Done units are JOULES however its base units are Nm.

Area under a Force-distance graph = Work done

Work Done = Energy transferred 

"Tension in the spring/wire is proportional to its extension from its natural length, provided the extension is not to great." 

Stretching force (F) =spring constant (K)  X extension (x) 

The spring constant is sometimes called the stiffness.

Force extension graph.

Elastic potential energy = 0.5 X Stretching force X extension  (AREA UNDER GRAPH)

PE LOST = KE GAINED 

"Energy cannot be created or destroyed only transferred from one for the another."

Gravitational potential energy = mgh 

Kinetic energy = 

Power is the rate of energy transfer.

Power = work done / time.

Power is measured in WATTS.

1 Watt = 1 joule per second

Static electricity is caused by the transfer of electrons for one object to another.

Neutral atoms can lose or gain electrons these atoms become positively or negatively charged. 

These charged atoms are called ions. 

GAIN ELECTRONS = - VE 

LOSE ELECTRONS = +VE

Current = Rate of flow of charge 

Charge = current X time 

Charge is measured in Coulombs.

Volume = Al 

Number of free electrons per m = nAl

Charge = nAle

As current = charge/ time 

I= nale/t 

As v = l/t 

Therefore I= nAve 

Free electrons collide with lattice ions. 

Kinetic energy is transferred from the electrons to the ions therefore energy is transferred. 

(I = nAve )

• number of charge carriers per m
• cross sectional area of conductor
• The drift speed of the charge carrier 
• Charge on an electron

What type of charge carriers carry electricity in a gas? 

• Electrons and positive ions  

"The potential difference between 2 point in a circuit when 1 joule of work in transferring 1 coulomb of charge from 1 point to the other. "

Units: V = Jc

• Semi-conductor Diode                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

• filament lamp                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              

• metal wire at constant temperature

"Voltage is proportional Current provided temperature is constant."

Ohms law graph 

"Resistance of a conductor is the ratio of p.d applied across it, to the current passing through."

Resistance is measured in ohms (       ).

A superconductor is a material with zero resistance.

As there are no collisions in a superconductor there is no energy transferred therefore no heat lost. 

For a material to become a superconductor must be cooled below its transition temperature. 

To cool material use liquid nitrogen. 

IN SERIES: 

• Current is the same at all points 
• Voltage splits 
• R = R + R 

IN PARALLEL:

• current splits up 
• Voltage stays the same.
•            

Emf = electromotive force 

Emf is the total work done by a cell per unit charge 

V = energy delivered per unit charge to external                circuit

E= energy supplied per unit charge to circuit from           chemical energy of cell.

Ir= Energy lost in internal resistance