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Define density.
A smooth pebble, made from uniform rock, has the shape of an elongated sphere as shown in the figure below.
The length of the pebble is 
. The cross-section of the pebble, in the plane perpendicular to , is circular with a maximum radius 
.
A student investigating the density of the rock makes measurements to determine the values of , and the mass 
of the pebble as follows:
State the name of a measuring instrument suitable for making this measurement of L.
Determine the percentage uncertainty in the measurement of r.
The density 
of the rock from which the pebble in (b) is composed is given by
where 
is an integer and 
is a constant, with no units, that is equal to 
.
Use SI base units to show that is equal to 
.
Calculate the percentage uncertainty in .
Determine with its absolute uncertainty. Give your values to the appropriate number of significant figures.
.
.
.
