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GCSE Unit 2
Mechanics, Electricity and
Nuclear Processes

Summary Notes



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Representing and Measuring Motion

· For an object moving at a steady speed, the distance it travels and the time it takes are related as

Speed = distance travelled (metre, m) ¸ time taken (second, s)
(metre/second, m/s) (metre, m) (second, s)

· When an object moves in a…

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Forces and Acceleration

· In general, objects experience one or more physical forces acting on them. The individual forces
are combined, taking into account size and direction, to give an unbalanced or resultant force
which acts in a particular direction.

· This unbalanced force will affect the movement of the…

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Frictional Forces and Nonuniform Motion

· A force of friction acts when an object moves through air or water, or when solid surfaces slide
(or tend to slide) across each other. The direction of this force of friction is always opposite to
the direction in which the object or surface…

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Work, Energy and Power

· When a force moves an object through a certain distance, energy is transferred and work is

work done = energy transferred = force applied ´ distance moved in direction of force
(joule, J) (newton, N) (metre, m)

· Power is the rate of energy…

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Gravitational Potential Energy and Kinetic Energy

· Gravitational potential energy (GPE) is the energy stored by an object because of the height to
which the object has been lifted against the force of gravity. Lifting an object at a steady speed
requires a force equal to the weight of the…

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· Momentum is proportional to both the mass and the velocity of on object. Momentum has both
magnitude (size) and direction, and is therefore, like velocity, a vector quantity. Momentum,
mass and velocity are related as shown:

momentum = mass ´ velocity
(kilogram metre/second, kg m/s) (kilogram, kg) (metre/second,…

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Atomic Structure

· atoms have a small central nucleus made up of protons and neutrons around which there are

· the mass number or nucleon number is the total number of protons and neutrons in the nucleus

· the atomic number or proton number is the number of protons…

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Types of Radioactivity

· Radioactivity occurs as a result of changes in the nuclei of atoms. Radioactive isotopes
(radioisotopes or radionuclides) are atoms with unstable nuclei. Unstable nuclei can decay by
emitting a radioactive particle, either alpha (a), beta (b) or gamma (g). The nucleus formed as a
result of…

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Properties and Uses of Radioactivity

· Radioactivity is a random process in that we cannot say for sure whether one particular nucleus
will decay in the next second. However, the number of nuclei and hence the activity (i.e.
number of decays occurring in 1 second) of a large sample decreases…


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