Friction, Air-resistance / Drag, Tension, Normal contact force, Upthrust
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What are some examples of non-contact forces?
Gravitational force, Electrostatic force, Magnetic force
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What is the difference between mass and weight?
Mass is constant and is the amount of matter contained in an object whereas weight is the force acting on an object due to gravity
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What is a resultant force?
More than one force acting on an object that can be seen as one single force that has the same effect as all the forces acting together
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What is the moment of a force?
When a force causes an object to rotate about a pivot point
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What is upthrust?
The upwards force exerted by a fluid on a submerged object
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What are the differences between distance, displacement and speed/velocity?
Distance - a scalar quantity Displacement - Vector quantity Speed - The measurement of how fast an object is travelling and is a scalar quantity Velocity - vector quantity
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What does Newton's first law state?
An object will remain in the same stste of motion unless acted on by an external force
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What does Newton's second law state?
The acceleration of an object is proportional to the resultant force acting on an object and inversely proportional to the mass of the object
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What does Newton's third law state?
For every action there is an equal and oposite reaction - when one objet exerts a force on another, the other objet exerts one back
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What is the principle of conservation of motion?
In a closed system, the total momentum before an event is equal to the total momentum after
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What is specific heat capacity?
The amount of energy required to raise the temperature of one kilogram of the substance by one degree celsius
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How can unwanted energy transfers be reduced?
Reduce friction as it produces heat / Tightening any loose parts which prevent unwanted vibration that waste energy as sound
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What is each coloured wire in mains electricity called and what do they do?
Brown - Live wire which carries the current to the appliance Blue - Neutral wire which carries the current away Green/yellow - Earth wire which prevents electric shocks as it sends any free electricity to the nearest mains supply
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What are the properties of alpha particles?
Most ionising and is absorbed by a few centimetres of air or a thin sheet of paper
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What are the properties of beta particles?
Some what ionising and is absorbed by a few millimetres of aluminium
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What are the properties of gamma rays?
Not very ionising and can pass through many centimetres of lead and many metres of concrete
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What is the half life of a radioactive isotope?
The (average) time that it takes for half if the nuclei to decay
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What is nuclear fission?
The splitting of a large, unstable nucleus that usually only occurs after the unstable nucleus has gained an electron
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What happens during nuclear fission?
The nucleus splits into two smaller nuclei and also emits 2 or 3 neutrons, gamma rays and energy
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What happens during nuclear fusion?
Two lighter nuclei join together to form a heavy nucleus. Some of the mass into energy and some of this energy may be emitted as radiation
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Why is nuclear fusion hard to manufacture?
It requires extremely high temperatures and pressures in order to overcome the electrostatic repulsion as well as to bring the positive nuclei close enough together for fusion to take place
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What is the nuclear equation for when an alpha particle is emitted?
The mass number is reduced by 4 while the atomic number is reduced by 2
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What is the nuclear equation for beta decay?
The mass number stays the same whereas the atomic number is increased by 1
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