A 10 kg rock that has been dropped from a 60 meter high cliff experiences a average force of air resistance of 30 N. Calculate the KE at the bottom of the fall.

Question

A 10 kg rock that has been dropped from a 60 meter high cliff experiences a average force of air resistance of 30 N.  Calculate the KE at the bottom of the fall.

so KE=PEgravity 5880 is the PE but no friction force deducted...do I just subtract 30N?
  my book is not clear...

bobpursley · Accepted Answer

KE at bottom=PE at top - friction=PE at top - forcefriction*height

mssailormouth · Answer

so 60 x 30 5880-1800=4080