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Page 1

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Turning forces - Moments
08 April 2012
12:22




A spanner as an example has a turning effect on a nut. A spanner has a long handle means less force needs to
be exerted
The moment of the force or the turning effect can be increased by
o Increasing the size…

Page 2

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Centre of mass
08 April 2012
12:25




For a racing car, the weight must be as low as possible or it would overturn when cornering at high
speeds
The centre of mass of an object is the point where its mass may be thought to be concentrated.
The centre of…

Page 3

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Moments in balance
08 April 2012
12:29


The sum of all clockwise moments about any points = the sum of all anticlockwise moments about that point

o This is the principle of moments.




Physics Page 3

Page 4

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Stability
08 April 2012
12:32




Stability and safety
o Tractor safety
A tractor doesn't topple over because the line of action of its weight acts
within its wheelbase. If it is tilted more, it will topple over when the line of
action of its weight acts outside its wheelbase. Its…

Page 5

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Circular motion
08 April 2012
12:33


For an object moving in a circle at constant speed, at any instant:
o The object's velocity is directed along a tangent to the circle
o Its velocity changes direction as it moves round
o The change of velocity is towards the centre of…

Page 6

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Gravitational attraction
08 April 2012
12:34



The Earth exerts a force of gravity on all of us; any two objects exert a force of gravitational
attraction on each other. The force depends on the mass of each object. The Earth is a massive
object so its force of gravitational attraction…

Page 7

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Planetary orbit
08 April 2012
12:36


Planets orbit the sun in elliptical orbits. Things always orbit larger things. The
centripetal force on the orbiting object is due to the force of gravitational
attraction between it and the larger object.
The force of gravity on a planet such as Earth is…

Page 8

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Satellites
08 April 2012
12:38
Satellite orbits
o If the speed of a satellite is too low, it will fall to the ground
o If its initial speed is too great, it will fly off into space
o At the correct speed, it orbits the Earth
A satellite in a…

Page 9

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Light and sound - Reflection
08 April 2012
12:40


o A real image can be projected on a screen by focusing light rays onto the
screen. They are formed where rays of light (from the same point on the
object) cross, so they can be formed on a screen.

The…

Page 10

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Curved mirrors
08 April 2012
12:43


The concave mirror
o When you look closely at it, you should see an enlarged image of your face
o Retreat from the mirror and your image will retreat and become blurred
o Keep moving and your image will reappear upside down and very…

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