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- Slide 1
- AQA P2 Physics Booster 2012 Specification E Ralls
- Slide 2
- Remember your units: Weight = newtons (N) Acceleration = m/s 2 Work done = joules (J)
- Slide 3
- P2.1: Motion
- Slide 4
- Speed = Distance Time This will not be on your data sheet
- Slide 5
- Distance time graphs
- Slide 6
- Speed vs. Velocity Speed is simply how fast you are travelling Velocity is speed in a given direction This car is travelling at a speed of 20m/s This car is travelling at a velocity of 20m/s east
- Slide 7
- Velocity-time graphs 80 60 40 20 0 10 20 30 40 50 Velocity m/s Time (s) accelerating constant speed/velocity accelerating decelerating
- Slide 8
- Acceleration vs. Deceleration Remember, if you are asked to work out the deceleration of an object, you use the same equation as you would to work out acceleration.
- Slide 9
- P2.2: Forces
- Slide 10
- Newton said: Objects continue to move in a state of constant velocity unless acted upon by an external net force. 1 ST LAW.
- Slide 11
- Newton Astronauts need to beware!
- Slide 12
- Newton also said: Every action has an equal and opposite reaction. - His 3rd law. Which explains why guns recoil and how rocket engines work.
- Slide 13
- Another example of the third law; this time to stop the astronaut moving.
- Slide 14
- Resultant Force When the resultant force on an object is not zero, movement depends on the size and direction of the resultant force.
- Slide 15
- Resultant Force 60N 20N 40N
- Slide 16
- Acceleration The acceleration of an object depends on the size of the resultant force. If the resultant force is zero the object will remain motionless or continue at a constant speed. Wind 2N Engine 4N Air resistance 3N Resultant Force 3N
- Slide 17
- Braking Force The braking force needed to stop a vehicle is dependant on: The velocity of the vehicle when the brakes are first applied. The mass of the vehicle.
- Slide 18
- Stopping Distance Stopping distance Thinking distance Braking distance
- Slide 19
- Stopping Distance
- Slide 20
- Factors Affecting Stopping Distance Tiredness, alcohol and drugs The speed that the vehicle is travelling Adverse road conditions Poorly maintained vehicle
- Slide 21
- Weight and Mass Mass = the quantity of matter in an object Weight = the force of gravity on an object The gravitational field strength of Earth is about 10N/kg
- Slide 22
- Weight and Mass
- Slide 23
- Air Resistance
- Slide 24
- Elastic Potential Energy An elastic object such as a spring stores elastic potential energy when stretched or squashed. Work is done on an elastic object when its shape changes and it stores elastic potential energy. Energy transferred by a force
- Slide 25
- Hookes Law The extension of an elastic object is directly proportional to the force applied to it Increase in length
- Slide 26
- P2.3: Work, Energy and Momentum
- Slide 27
- Energy and Work When an object is moved by a force we say work is done on the object by the force. The force transfers energy to the object.
- Slide 28
- Gravitational Potential Energy Transfers Energy stored in an object because of its position in the Earths gravitational field. The equation: change of GPE = weight x change in height joules, J newtons, N metres, m
- Slide 29
- change of GPE = weight x change in height joules, J newtons, N metres, m
- Slide 30
- You wont always be given a weight. Sometimes you will need to use this equation: joules, J kilograms, kg newtons per kilogram, N/kg metres, m
- Slide 31
- Kinetic Energy
- Slide 32
- Kinetic energy 1.If an object of mass 15kg is travelling at 5m/s, how much kinetic energy does it have? 2.A car is travelling at 30m/s and has kinetic energy of 450kJ, what is its mass? 3. A tennis ball has a mass of 0.06kg and has kinetic energy of 2.94kJ when served, what is its speed? x 15 x 25 = 187.5J m=2xKE/v 2 =2x450000/900=1000kg v= (2KE/m) = (5.88/0.6)=3.13m/s
- Slide 33
- Momentum
- Slide 34
- Conservation of Momentum So long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions.
- Slide 35
- Conservation of momentum question Two trolleys collide and stick together. From the data below, calculate the velocity of the trolleys after the collision. trolley Atrolley B mass = 3 kgmass = 5 kg velocity = 8 m/svelocity = -4 m/s momentum = 24 kg m/s (3 x 8)momentum = -20 kg m/s (5 x -4) total momentum before collision = 4 kg m/s (24 + -20) mass after collision = 8 kg (3 + 5) momentum after collision = 4 kg m/s velocity after collision = momentum / mass = 0.5 m/s
- Slide 36
- Investigating momentum
- Slide 37
- Try these.. A trolley of mass 4kg moving at 10 m/s collides with a 2 kg trolley moving in the same direction at a velocity of 4m/s. they separate after the collision and the 4 kg trolley slows to 7m/s. What is the final speed of the other trolley? (hint draw diagrams of momentum before and after) a trolleyA of mass 1kg is travelling at 2m/s towards another trolleyB of mass 4kg which is travelling towards it at a velocity of 3m/s. On collision they stick together. What is their final combined velocity and in which direction do they travel together? (care with negatives) 10m/s 2m/s to the left
- Slide 38
- Explosions and Momentum (mass of A x velocity of A) = - (mass of B x velocity of B)
- Slide 39
- Changing Momentum Cars have crumple zones to increase impact time on collision. If you increase the impact time, it will decrease the impact force.
- Slide 40
- P2.4: Current Electricity
- Slide 41
- Van de Graaff generator
- Slide 42
- When you rub two different insulated materials against each other they become electrically charged. This only works for insulated objects. Charging by Friction
- Slide 43
- Two charged rods of different materials will attract each other if they have a different charge. Two rods made of the same material will repel each other due to having the same charge. Like charges repel: unlike charges attract
- Slide 44
- Circuit Symbols V Battery Cell Fuse Resistor LDR Voltmeter Ammeter Variable resistor Diode Switch (open) Bulb (lamp) A
- Slide 45
- Resistance is measured in ohms ()
- Slide 46
- Ohms Law The current flowing through a resistor at a constant temperature is directly proportional to the voltage across the resistor. So If you double the voltage, the current also doubles.
- Slide 47
- Ohmic resistor Filament lamp Diode The filament lamp does not follow Ohms Law. Its resistance increases as the temperature of its filament increases. The diode has a very high resistance in one direction. This means that current can only flow in the other direction.
- Slide 48
- Series Circuits The same current passes through components in series with each other If the current through the lamps is 0.12A, what is the current through the cell? 0.12A
- Slide 49
- Series Circuits The total potential difference of the voltage supply in a series circuit is shared between the components. If the potential difference of the cell is 1.2V and the potential difference of across one lamp is 0.8V, what is the potential difference across the other lamp? 0.4V 1.2V 0.8V 0.4V
- Slide 50
- Series Circuits The total resistance of components in series is equal to the sum of their separate resistances. What is the total resistance if one lamp in series has a resistance of 2 and the other has a resistance of 3 ? 55 22 33
- Slide 51
- Parallel Circuits The total current through the whole circuit is the sum of the currents through the separate components. A1A1 If ammeter A 1 reads 0.4A and A 2 reads 0.1A, what would A 3 read? 0.3A A2A2 A3A3 0.4A 0.1A 0.3A
- Slide 52
- Parallel Circuits For components in parallel, the potential difference across each component is the same. If the potential difference of the cell is 6V, the potential difference across each lamp will also be 6V. 6V
- Slide 53
- P2.5: Mains Electricity
- Slide 54
- Direct current The battery in a torch uses direct current. This means it moves in one direction only.
- Slide 55
- Direct Current
- Slide 56
- Alternating Current Mains electricity uses an alternating current. This means that the current repeatedly reverses direction. The UK mains supply being about 230 V. It has a frequency of 50 Hz (50 hertz), which means it changes direction, and back agai