# p2

• Created by: jl45
• Created on: 31-03-16 14:15
whats the difference between speed and velocity?
Speed is the distance traveled by an object where as, velocity is distance traveled by an object per unit time in a particular direction.
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Explain how to calculate speed from a distance-time graph
This equation shows the relationship between speed, distance travelled and time taken: speed = distance travelled ÷ time taken.For example, a car travels 300 m in 20 s. Its average speed is: 300 ÷ 20 = 15 m/s
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write down the formula for acceleration.
Acceleration is the rate at which an object changes its speed. It's calculated using the equation: acceleration = change in velocity/ time taken.
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Give an example of acceleration
A bus accelerates from 5 m/s to 25 m/s in 10s To calculate its acceleration, first find the change in speed. This is 25m/s - 5m/s = 20m/s Acceleration = 20m/s ÷ 10s = 2m/s2
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how is stationary movement presented on a distance time graph?
When an object is stationary, the line on the graph is horizontal.
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how is steady speed presented on a distance time graph?
When an object is moving at a steady speed in a straight line, the line on the graph is straight but sloped.
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the steeper the line on a distance time graph the
The greater the speed of the object.
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how is constant velocity presented on velocity time graph?
When an object is moving with a constant velocity, the line on the graph is horizontal.
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how is constant acceleration presented on a velocity time graph?
When an object is moving with a constant acceleration, the line on the graph is straight but sloped.
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The steeper the line on a velocity time graph the ...
the greater the acceleration of the object.
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what does a line sloping downwards on a velocity time graph mean?
Notice that a line sloping downwards - with a negative gradient - represents an object with a constant deceleration (slowing down).
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what do flat sections on a velocity time graph represent?
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what does a curve on a velocity time graph represent?
changing acceleration
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what is the gradient of a velocity time graph?
acceleration.
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Explain how to find acceleration from a velocity time graph.
a = (v – u) ÷ t . For example, a car accelerates from 25 m/s to 35 m/s in 5 s Its velocity changes by 10 m/s (35 – 25) So its acceleration is 10 ÷ 5 = 2 m/s2
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how do you find the velocity on a distance time graph?
The velocity at any point is simply found by reading the value of the velocity axis
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how do you find the distance on a velocity time graph?
The distance travelled in any time interval is equal to the area under the graph. For example the distance travelled between t= 80s and t= 100s equal to the shaded area, which i equal to 20X50= 1000 m
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Explain the difference between mass and weight and their units.
Weight is not the same as mass. Mass is a measure of how much stuff is in an object. Weight is a force acting on that stuff.Weight is measured in newtons, N Mass is measured in kilograms, kg
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If an object has zero resultant force on it, can it be moving? can it be accelerating?
A stationary object remains stationary if the sum of the forces acting upon it - resultant force - is zero. A moving object with a zero resultant force keeps moving at the same speed and in the same direction.
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Write down the formula relating resultant force and acceleration and give an example.
resultant force (newton, N) = mass (kg) × acceleration (m/s2). For example, the force needed to accelerate a 10kg mass by 5m/s2 is: 10 x 5 = 50N
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What is terminal velocity?
he constant speed that a freely falling object eventually reaches when the resistance of the medium through which it is falling prevents further acceleration.
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describe the 3 stages of falling
1) At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards. 2)As it gains speed, the object's weight stays the same, but the air resistance on it increases. There i
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describe the 3 stages of falling (2)
is a resultant force acting downwards. 3Eventually, the object's weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.
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What are two different parts of the overall stopping distance of a car?
The stopping distance depends on two factors: Thinking distance - It takes time for a driver to react to a situation. During this reaction time the car carries on moving. The thinking distance is the distance travelled in between the driver realising
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What are two different parts of the overall stopping distance of a car? ?(2)
he needs to brake and actually braking.
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write down the formula for work done. A crazy dog drags a big branch 12m over the next door neighbours front law, pulling with a force of 535 N. How much work was done?
The amount of work done is expressed in the equation: work done = force x distance so 12m X 535 N =6,420 J
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A 4 kg cheese is taken 30 m up a hill before being rolled back down again. If g=10N/kg how much gravitational potential energy does the cheese have at the top of the hill?
gravitational potential energy = mass X g X height so 30X10X4 = 1,200 J
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Whats the formula for kinetic energy and give an example.
KE = ½ mv2 ( to the power of 2) . V = the speed in metres per second, m/s .For example, what is the kinetic energy of a 1000 kg car travelling at 5 m/s? KE = ½ × 1000 × 52 = 500 × 25 = 12500 J
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write down the equation that relates the force on a spring and its extension
F = k × e F is the force in newtons, N k is the 'spring constant' in newtons per metre, N/m e is the extension in metres, m
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what is the limit of proportionality?
This equation works as long as the elastic limit (the limit of proportionality) is not exceeded. If a spring is stretched too much, for example, it will not return to its original length when the load is removed.
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calculate the power output of that 78 kg sheep when she runs 20m up a staircase in 16.5 seconds
power= work done (or energy transferred) / time taken , so 20/16.5 = 1.21 W
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write down the formula for momentum, if the total momentum of a system before collision is zero what is the total momentum of the system after the collision.
momentum = mass X velocity , zero because momentum before = momentum after( conversation of momentum)
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what is the advantage of using regenerative braking systems?
the motor acts as an electric generator, converting kinetic energy into electric energy that is stored as chemical energy in the vehicles battery. This is the advantage of regenerative brakes- they store the energy of braking rather than wasting it.
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Explain how seat belts, crumple zones, side impact bars and air bags are useful in cars.
All these features reduce injuries to the people in the car by absorbing energy when they change shape. Car crash simulation Car crash simulation As they deform they increase the amount of time the person takes to come to a stop. This reduces the
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Explain how seat belts, crumple zones, side impact bars and air bags are useful in cars. (2)
acceleration and force on the person, so reducing injury.
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Describe the effect on the top speed of a car of adding a roof box. Explain your answer.
A car with a roof box has increased air resistance and fuel consumption and a downhill skier puts wax on the skis to reduce friction and so increase the top speed.
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what causes the build of static electricity? which particles move when static builds up?
Some insulating materials become electrically charged when they are rubbed together. Charges that are the same repel, while unlike charges attract.
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which particles move when static builds up?
Negatively charged particles called electrons move from one material to the other The material that loses electrons becomes positively charged The material that gains electrons becomes negatively charged Both materials gain an equal amount of charge,
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True or false: the greater the resistance of an electrical component, the smaller the current the current through it
true
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240 C of change is carried though a wire in a circuit in one minute. How much current flowed in the wire?
current= charge/ time so 240/ 1= 240 kc
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what formula relates work done, potential difference and charge?
W = QV Where W is the work done Q is the charge on the object V is the potential difference
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Explain how resistance of a component changes with its temperature in terms of ions and electrons
When an electrical charge flows through a resistor, some of the electrical energy is transferred to heat energy and the resistor gets hot. This heat energy causes the ions in the conductor to vibrate more. With the ions jiggling around its more
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Explain how resistance of a component changes with its temperature in terms of ions and electrons (2)
difficult for the charge- carrying electrons to get through resistors- the current cant flow as easily and the resistance increases
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What p.d is required to push 2 A of current through a 0.6 ohms resistor?
P.D = work done/charge 2/0.6= 3.33
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Give 3 applications of LEDs
Piezo sounders, buzzers, bells, loudspeakers and sirens are used to convert electricity into sound. Microphones convert sound into electricity.
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Describe how the resistance of an LDR varies with light intensity. Give an application of an LDR
Their resistance decreases as the light intensity increases.LDRs are also useful for controlling how long the shutter should remain open on a digital camera.
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An AC supply of electricity has a time period of 0.08s . What is its frequency?
Frequency = 1 ÷ period so 1/0.08 = 12.5 Hz
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Name the three wires in a three-core cable + their colours
earth wire ( green and yellow) , live wire ( brown) , neutral ( blue
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Explain fully how a fuse and earth wire work together
The earth wire creates a safe route for the current to flow through if the live wire touches the casing.so that the current goes through the earth wire instead of causing an electric shock. A strong current surges through the earth wire because it
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Explain fully how a fuse and earth wire work together (2)
has a very low resistance. This breaks the fuse and disconnects the appliance.
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how does an RCCB stop you from getting electrocuted?
Residual current circuit breakers, RCCBs, protect some circuits. They detect a difference in the current between the live and neutral wires. RCCBs work much faster than fuses do.
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Which uses more energy a 45 W pair of hair straighteners used for 5 minutes, or a 105 W hair dryer used for 2 minutes?
Energy transferred= power X time so 45 X 300= 13,500 J ; 105 X 120 = 12,600 J so hair straighteners ( convert minutes into seconds and kilowatts into watts by multiplying by 1000)
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Find the appropriate fuse ( 3 A , 5 A or 13 A ) for a toaster rated at 230 V , 1100 W
power = current X p.d so to find the current 1100 W/230 V = 4.7 so 5 amp fuse needed
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Find the appropriate fuse ( 3 A , 5 A or 13 A ) an electric heater rated at 230 V , 2000 W
2000 W/230 V = 8.69 so 13 Amp fuse would be needed
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Calculate the energy transformed by a torch using a 6V battery when 530 C of charge pass through .
Energy transformed = charge X potential difference so 530 C X 6 V= 3,180 J
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Explain how the experiments of of Rutherford and Marsden led to the nuclear model of the atom.
A scientist called Rutherford designed an experiment to test the plum pudding model. It was carried out by his assistants Geiger and Marsden. A beam of alpha particles was aimed at very thin gold foil and their passage through the foil detected.
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Explain how the experiments of of Rutherford and Marsden led to the nuclear model of the atom. (2)
he scientists expected the alpha particles to pass straight through the foil, but something else also happened. Some of the alpha particles emerged from the foil at different angles, and some even came straight back. The scientists realised that the
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Explain how the experiments of of Rutherford and Marsden led to the nuclear model of the atom. (3)
positively charged alpha particles were being repelled and deflected by a tiny concentration of positive charge in the atom. As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom.
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name the the relative mass and charge of the three basic subatomic particles
proton: mass = 1 , charge = +1 neutron: mass = 1 charge= 0, electron mass= 1/2000 charge= -1
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true or false: radioactive decay can be triggered by certain chemical reactions?
false
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What type of subatomic particle particle is a beta particle?
beta particles are electrons, alpha particles are helium nuclei , and gamma rays are are very short wavelength EM waves
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list two places where the level of background radiation is increased and why.
Cosmic rays - radiation that reaches the Earth from space .Rocks and soil
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Name 3 occupations that have increased risk of exposure to radiation
Cosmic rays , Rocks and soil , Living things
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What is the definition of half life?
Half life is the average time it takes for the number of nuclei in a radioactive isotope sample to halve
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give an example of how gamma radiation can be used in medicine
since high doses of gamma rays will kill all living cells, they can be used to treat cancers
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which is the most dangerous form of radiation if you eat it? why?
beta particles?
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Describe the precautions you should take when handling radioactive sources in laboratory
wearing protective clothing keeping as far away as is practicable - for example, by using tongs keeping your exposure time as short as possible keeping radioactive materials in lead-lined containers, labelled with the appropriate hazard symbol.
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Describe nuclear fission of uranium 235 and explain how the chain reaction works
Fission is another word for splitting. The process of splitting a nucleus is called nuclear fission. When a uranium-235 or plutonium-239 nucleus is hit by a neutron, the following happens: the nucleus splits into two smaller nuclei, which are
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Describe nuclear fission of uranium 235 and explain how the chain reaction works (2)
adioactive two or three more neutrons are released some energy is released.
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What is the main environmental problem associated with nuclear power?
Like fossil fuels, nuclear fuels are non-renewable energy resources. And if there is an accident, large amounts of radioactive material could be released into the environment. In addition, nuclear waste remains radioactive and is hazardous to health
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What is the main environmental problem associated with nuclear power? (2)
to health for thousands of years. It must be stored safely.
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What is nuclear fusion? why is it difficult to construct a working fusion reactor?
nuclear fusion is the joining of smaller nuclei to make larger ones. Nuclear fusion happens in stars and fusion bombs. extremely high temperatures are needed.
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Describe the steps that lead to the formation of a main sequence star ( like our sun)
1) Stars form from massive clouds of dust and gas in space. The animation summarises how this happens. 2) Gravity pulls the dust and gas together. 3) As the gas falls together, it gets hot. A star forms when it is hot enough for nuclear reactions to
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Describe the steps that lead to the formation of a main sequence star ( like our sun) (2)
start. This releases energy, and keeps the star hot. 4 During its 'main sequence' period of its life cycle, a star is stable because the forces in it are balanced. The outward pressure from the expanding hot gases is balanced by the force of the sta
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Describe the steps that lead to the formation of a main sequence star ( like our sun) (3)
force of the star’s gravity. Our Sun is at this stable phase in its life. 5) Gravity pulls smaller amounts of dust and gas together, which form planets in orbit around the star.
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Why will our star never form a black hole?
No. Stars like the Sun just aren't massive enough to become black holes.
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## Other cards in this set

### Card 2

#### Front

Explain how to calculate speed from a distance-time graph

#### Back

This equation shows the relationship between speed, distance travelled and time taken: speed = distance travelled ÷ time taken.For example, a car travels 300 m in 20 s. Its average speed is: 300 ÷ 20 = 15 m/s

### Card 3

#### Front

write down the formula for acceleration.

### Card 4

#### Front

Give an example of acceleration

### Card 5

#### Front

how is stationary movement presented on a distance time graph?