Physics P3 Revision notes

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  • Created by: Bhavik
  • Created on: 13-05-11 11:36
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Physics revision notes
Physics Revision notes
The force applied on something has an effect on the turning effect.
The long handled spanners are better than short handled ones because they have a
larger moment.
Increasing the size of the force or using a longer length both increase the moment.
A crowbar is a lever. The weight is called a load. The force applied is the effort and the
point about which the crowbar turns it the pivot.
Moment (Newton Metres) = Force (Newtons) x Perpendicular distance from the
pivot to the line of action of the force
The centre of mass of an object is the point where its mass may be thought to be
concentrated.
A rectangle has the centre of mass where the two lines of symmetry meet
The same for an equilateral triangle.
A seesaw is an example in which the clockwise and anti clockwise moments might
balance each other out.
W1d1 = W2d2
The seesaw is an example of the principle of moments. This states that an object in
equilibrium:
The sum of all the clockwise moments about any point = the sum of all the
anticlockwise moments about that point
EG. If W2 = 4N and D1 = 0.25m and D2 = 0.2 m
Then W1 = W2d2/d1 = 4x0.2/0.25 = 3.2 N
If the centre of mass is outside the base of an object then it will topple over.
3 examples of things tested for stability are Tractors, Buses and high chairs for
babies.
An object moving at a constant speed at any instant: The object's velocity is directed
along a tangent to the circle, its velocity changes direction as it moves around, the
change of velocity is towards the centre of the circle. Therefore the object
accelerates continuously towards the centre of the circle.
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Physics revision notes
We say that the resultant force is a centripetal force because it always acts towards
the centre of the circle.
The centripetal force on a vehicle moving round a roundabout isis due to the friction
between the tyres and the road
The centripetal force on an aircraft circling round is due to the combined effect of its
weight and the lift force on it. The centripetal force is a result of these two forces.…read more

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If you look in a mirror and you are seeing a tall thin image of yourself then you are
looking in a convex mirror which is one that bends out
If you are looking and you see a short broad image of yourself then it's a concave
mirror which bends in.
A plane mirror will show an exact image of yourself
An image is seen due to the reflection of light by the mirror.…read more

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For an object between the focal point and the mirror, the reflected rays form and
upright VIRTUAL image. The image is magnified behind the mirror.
The convex mirror is used for rear view mirrors in cars. They have a wider field of view
than with a plane mirror. The image viewed is VIRTUAL and SMALLER than the image
is shown.…read more

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With the object nearer to the lens than the principal focus, a MAGNIFIED VIRTUAL
image is formed. But you can only see the image when you look into the lens from
the other side to the object. The lens acts as a magnifying glass in this situation.
The position and nature of the image formed by a lens depends on the focal length
of the lens and the distance from the object to the lens.…read more

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Increasing the loudness of a sound makes the waves taller which means that you
have increased the amplitude.
Increasing the frequency of a sound is the number of waves per second which
increases the pitch.
An instrument resonates at frequencies when it vibrates matter.
A wind instrument such as a flute is designed so that the air inside resonates when
played.…read more

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The direction of the force is always at right angles to the wire and the field line also if
the direction of the force is reversed then so is the current's direction and the
magnetic field.
And electric motor is designed to use the motor effect. Changing the current can
make a motor faster.
A motor is usually a rectangular coil of insulated wire that is forced to rotate. The coil
is connected via two graphite brushes to the battery.…read more

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Physics revision notes
A transformer has two coils of insulated wire both around the same iron core. When
a AC current passes through one current, an AC current is produced in the secondary
coil.
AC current passing through the primary coil produces and AC magnetic field.
The lines of the AC magnetic field pass through the secondary coil inducing an AC
current. If a lamp is connected to a secondary coil, then it will work, even if it isn't
directly connected to the circuit.…read more

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Stars form out of clouds of dust and gas.
The particles in the clouds gather together under their own gravity, the clouds merge
and become a protostar which is a star to be.
As the protostar becomes denser, it gets hotter and if it becomes hot enough then
the hydrogen nuclei and other light elements fuse together and energy is released in
the process in the form of heat and light energy. This is a star.…read more

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