# Physics

Get Started. It's Free Physics ## 1. Mains electricity

### 1.1. Battry = DC (direct current), Mains = AC (Alternating current)

1.1.1. AC - Electrons repeatedly reverses direction

1.1.1.1. 50 Hertz, Peak 325 volts +ve to low -325 volts -ve, average 230 volts.

### 1.2. Mains have live and neutral wire, Neutral wire earthed at 0 volts, Live wire +ve and -ve.

1.2.1. Cables and plugs.

1.2.1.1. 2-3 insulated copper wires

1.2.1.1.1. New node

1.2.1.2. Earth Green + Yellow, Neutral Blue, Live is brown.

1.2.1.2.1. surrounded by insulator, flexable material.

### 1.4. Fuses

1.4.1. A fuse conatins a thin wire which heats then melts cutting off current if too much pases though it.

1.4.1.1. Rating of fuse is max current that can pass though it with out melting the fuse wire.

### 1.5. Circuit breaker

1.5.1. Electromagnetic switch that opens and cuts off current if too much current pases though it, Faster than fuses and can be reset.

### 1.6. Power

1.6.1. Power = energy tansformed / Time

1.6.2. Power = Current * PD.

### 1.7. Electric current

1.7.1. rate of flow of charge.

1.7.1.1. charge flow in Coulombs = Current * times

1.7.1.1.1. Energy transformed = PD * Charge Flow.

## 2. Motion

### 2.1. Distance vs Time graph

2.1.1. Slope = Speed

2.1.2. Speed = Distance traveled

2.1.2.1. Devided by time

2.1.3. Steper slope = faster

2.1.4. Horizontal line = stoped

2.1.5. Speed is M/S (unless other wise stated)

## 3. Velocity & Acceleration

### 3.4. Velocity time graph

3.4.1. Slope = Acceleration.

3.4.1.1. Acceleration = Change in Velocity

3.4.1.1.1. Divided by time taken for change.

### 3.5. Slowing Down

3.5.1. Deacceleration or negitive acceleration

3.5.1.1. Body traveling at stedy speed is accelerating if direction is changing.

## 4. Velocity Time Graphs

### 4.3. Equation

4.3.1. The equation can be used to find acceleration in DTG & VTG.

## 5. Forces

### 5.1. Equal and opperset

5.1.1. Objects push or pull each other exert equal and opperset forces on each other.

5.1.1.1. Measured in Newtons

5.1.1.2. Friction acts between surfaces.

### 5.2. Resultant Force

5.2.1. Resultant force = 0 object remains stationary or continues to move in same direction with same speed.

5.2.1.1. When resultant force is not 0, And in same direction as movement of object, object accelerates.

5.2.1.1.1. If resultant force is not 0 and in opperset direction to movement of object it will decellerate.

### 5.3. Force and acceleration

5.3.1. Resultant force (N) = Mass (KG) x Acceleration (Ms squr).

5.3.1.1. Breaking force depends on velocity and mass of vehicle.

5.3.1.1.1. > velocity = > deceleration to stop in certain distance. > mass = > breaking force for deceleration.

5.3.2. Falling objects.

5.3.2.1. Weight of object = force of gravity, weight = mass * Gravity field strength.

5.3.2.1.1. Weight = force of gravity , Mass = quanty of matter.

## 6. Work energy & momentum.

### 6.1. when object moved my force, work is done on object by force,

6.1.1. Work done = Energy transfered

6.1.1.1. Work done (Joules) = Force (N) * Distance moved in direcetin of force (M).

6.1.1.2. Work done to overcome friction mainly transformed in to heat energy (Some sound).

6.1.1.2.1. kenetic energy of an moving object = 1/2 mass * Speed (Squared),

### 6.3. Momentum = Mass * Velocity

6.3.1. Momentum is concerved in any collision or explosion provided no external forces act on the objects.

6.3.1.1. Momentum has size and direction, two objects push each other appart they move appart with equal and opperset reaction.

6.3.2. Move time an impact takes the less force is exerted. Force = Change of momentum / by time taken.

6.3.2.1. New node

## 7. Static electricity

### 7.3. Electrons -ve

7.3.1. Only electrons can be transfered to and from an atom.

7.3.1.1. Adding electrons make an atom -ve, removing electrons makes an atom +ve.

7.3.1.1.1. Polythene rod when rubed become -ve, Perspect rod becomes +ve, it loses electron.

### 7.4. Current is the rate of flow of the electrical charge.

7.4.1. Metals conduct electricity becuase they contain delocalised electrons.

7.4.1.1. Insulatores can't conduct electriticy and all electrons are helled in their atoms.

7.4.1.1.1. A conduton and only chage if insulated from the ground,

7.4.1.1.2. To charge an infulated condutor it needs to be braught in to contat with a charged object.

7.4.2. Uses of static electricity, Paint sprayer, Percipitator in power station, photocopyer,

7.4.2.1. Build up of static electricty could cause spark, and an explison or fire. To eliminate static electricity use anti static materials or earth metal objects and pipes.

## 8. Current electricity

### 8.1. ammeter connected in series, Volt meter connected in parallel.

8.1.1. Risistance = Potential difference / Current

8.1.1.1. New node

### 8.2. Ohms law - Current though risistor is Directly proportional to PD accross the resistor.

8.2.1. Filiment lamp, resistance increaces as temperature increases

8.2.1.1. Diode, Forward risistance low, reverse risistance high.

8.2.1.1.1. Thermistor - Ristance decreases as temp increases (likes heat)

8.2.1.1.2. LDR - Risistance decreases as light intencity increases.

### 8.3. Series circuits,

8.3.1. Current the same though each component, PD add to give total PD

8.3.1.1. Resistance add to give total risistance,

8.3.2. Parallel circuits, total current is sum though component, PD is same though each component.

8.3.2.1. Bigger the resistance the smaller the current.

## 9. Nuclear

### 9.1. Nuclear reactions

9.1.1. Isotop pic find

9.1.1.1. Top = A = the number of protons and neutrons. Bottem = Z = Number of protons.

9.1.1.1.1. Reletive mass = Proton 1, Neutron 1, Electron 0.0005.

### 9.2. Relative Charge

9.2.1. Proton +1, Neutron 0, Electron -1.

9.2.1.1. Charged atom = Ion, Unequal number of protons and neutrons.

### 10.1. Unstable nucleus --> more stable after emitting Alpha, Beta, Gamma.

10.1.1. Alpha = 2 protons & 2 Neutrons, rel mass 4, Rel charge + 2.

10.1.2. Beta = Neutron changes to proton & beta, Emitted at high speed. Rel mass 0, Rel charge 1.

10.1.3. Emitted after alpha and beta, Uncharged no mass,

10.2.1. From cosmic rays x ray tubes, radioactive isotopes in envrioment.

10.2.1.1. New node

### 10.3. Descovery of nucleus

10.3.1. Rutherford, scattering alpha particles by fin metal foil, Most pass though, some deflected by the nucleus.

10.3.1.1. Nucleus positivly charged, as alpha's repelled, Smaller than atom as alphas pass though, where most of mass located.

10.3.1.1.1. New node

## 11. Nuclear fission

### 11.1. Nucleus splits in to two new smaller nuclei, Releases nutrons, energy is released, Can produce chain reaction.

11.1.1. Nuclear reactors use uranium 235 or plutoniu, 239.

11.1.1.1. New node