IB PHYSICS SUBSIDIARY LEVEL
FIELDS AND FORCES
SUMMARY
6.1
Gravitational force and field (2h)
The forces of attraction between two masses are along the line between their centres and equal size
and opposite directions.
The forces equal big G times mass one times mass two divided by the square of the distance
between their centres.
The force of gravity is an inverse square law with distance. At twice the distance the force is one
quarter as much.
The gravitational field at a point is the resultant gravitational force that 1 kg would receive.
The gravitational field near a mass equals big G times the mass divided by the distance squared
from the centre.
The gravitational field on the surface of a mass equals big G times the mass divided by the radius
square.
6.2
Electric force and field (3h)
The two types of charge are positive on protons and negative on electrons.
During charging by friction, electrons are rubbed off one object leaving it excess positive and onto
another object leaving it excess negative.
During all charging processes, the total charge before the process equals the total charge after the
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 Spring '11
 JamesInstor
 Physics, Force, Mass, Magnetic Field, Electric charge, South Pole

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