- P=Mv
- Momentum = Mass x Velocity
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Units: Kgms-1
- Mass is the same anywhere in the universe but weight is not.
- W=mg when g = gravitational field strength
- Overall stopping distance of a car depends on thinking distance and braking distance.
- Most materials will change shape when a small force is applied to them but will return to their original shape when then force is released.
- Materials which do this = elastic
- Not = plastic
- If we apply a load to a spring tiw ill extend, more we apply more it will extend
- When we remove, the load the spring retirns to its original length
- But if we apply to much, the spring will be damaged and willl not return, it is passed it’s ELASTIC LIMIT.
- Robert Jooke, fount extension is proportional to load provided el not exceeded = Hooke’s Law
- Can’t be created, just reused
- Changes from 1 type to another e.g. Kinetic to Heat
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Principle of Conservation of energy ➔Energy exists in different forms and can transfer between them. Everything need energy
- Different forms
- Fuels store chemical energy
- People and machines can convert this energy into other forms to allow them to do useful tasks.
- Energy us never lost or destroyed
- Always converted
- Forms of energy:
- Kinetic
- Heat
- Chemical
- Electrical
- Light
- Sound
- Gravitational Potential Energy
- Energy: Different Forms
- Conserved
- Required to do useful things
Potential Energy is affected by gravity, mass and height
- Potential energy is given to objects if they fall
- Objects have more potential energy if they are higher
- Objects have more kinetic energy if they move faster or have more mass.
- IE: PE = MGH
Kinetic Energy
- To do with movement
- The faster u go, the more Kinetic Energy
- Mass and Velocity affect kinetic energy.
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KE = ½ MV2
Energy:
Differnet Forms:
KE = ½ MV2
P.E = mgh
Conservation
Doing Useful things WORK.
Work:
Work Done = Energy transferred
Mechanical Work done = Force x distance
POWER
Rate at which work is done
Work Done/Time Taken = energy transfer/time taken
Unit = Watt = 1J/S
Momentum
Product of mass and velocity
VECTOR quantity
When 2 object act on each other, total momentum remains constant
Pressure
When forces act effect spread over an area.
Product is the force acting on an area: P=F/A
Increase pressure, decrease are / increase force
Hydraulics
Volume of liquid can’t be reduced by squeezing it. Liquids pass on any pressure that is applied
Liquids transmit pressure equally in all directions liquids can be used as FORCE MULTIPLIERS
Properties are used in hydraulic machines
Volume of gas can be reduced by squeezing because they can pass on some of the pressurem but not all of it because they can be compressed
E.g: If the input force is 10N and the input area is 0.1 m2 in a hydraulic jack, and the output area is 0.5 m2, then what is the maximum load that can be lifted?
First: what is the pressure on the oil = input force/input area = 10/0.1 = 100 N/M2
This pressure is transmitted thought the liquid:
Output force = Pressure x Output Area
100 x 0.5 = 50N
gas particles move about freely at high speed, in a solid particles vicrate and cannot change positions.
A solid has a fixed shape and volume. Particles = vibrate but cannot move
No attractions between particles in a gas.
Brownian motion = looking down a microscope into a chamber with smoke particles. Can see particles moving in a haphazard fashion which is because the air molecules are pushing it. Byt this I mean that the aprticles are being bombarded by air molecules and therefore it changes direction.
Boyles Law
For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume.
If the volume is halved, the pressure doubles
Presuure x volume always has the same value
P1 x V1 = P2 x V2
The gas laws:
Speed of molecules in a gas reduews as the temperature falls
Pressure is directly proportional to the Kelvin temperature (for a fixed mass of gas at constant volume. Similar relationship between volume and temperature: The volume is directly proportional to the temperature
PV/t = const
Turning effect of a force dpends on the size of the forace and the perpendicular distance from the point of application to the pivot.
Moment = Force x distance
Sum of clockwise moments = sum of anti-clockwise moments.
- Resistors get hot when electric current passes through them
- Voltmeters placed in parallel ammeters in series
- V = IR
- Current is a flow of charge
- It Transfers energy to the different components within the circuit
- We control current by adding or removing obstructions
- Resistance = V/I
- Ohm’s law states that current through a wire is directly proportional to the voltage across it unless temperature is not constant
- Bulb doe not obey Ohms Law its VI graph is not a straight line because as current increases the temperature changes
- P = VxI
- I = Q/t
- V = E/Q
- R = V/I
- P = VI
- P = E/T
- I = a
- Q = c
- T = s
- V = v
- P = w
- E = J
- R = Ohms
- Thermistor reduces resistance as temperature increases
Electrical Power is the rate of energy transfer in Watts
P = E/t
Or P = Current x P.D
Also IxV
E = VxIxT
Prove that P = VxI
P = E/T
P = Vq/(Q/I)
So P = VI
