Bees use electrostatic forces to both detect flowers and collect pollen

grains. As they fly through the air, they acquire a charge of approximately

$+30$ pC through friction with the air. Flowers and the pollen grains they contain tend to be negatively charged to about $-10$ fC$.$ Note: $1$ pC $=$

$1012$ C and $1$ fC $=1015$ C$.$

i$.$ Calculate the magnitude of the electrostatic force between a bee and

a grain of pollen separated by $5$ mm assuming the bee and pollen

grains are charged as above. $(2$ marks$)$

ii$.$ The mass of a grain of pollen is approximately $2501012$ kg$.$ At

what distance is the electrostatic force between the bee and the pollen

grain sufficient to overcome the gravitational force between the pollen

grain and Earth? $(6$ marks$)$

iii. If the bee collects $3000$ pollen grains, calculate the electrostatic force

between the bee and an uncollected pollen grain $1$ mm away $($with

charge $-10$ fC as before$).(2$ marks$)$