Question

a 60kg rock in on a mountain in banff national park breaks free from a ledge and falls down 500 meters to the bottom of the mountain the average air resistance is 150N what is the average acceleration of the rock?

Answer 1

Using Newton's law that  F = ma.

The force here is the net force.  The forces acting in opposite direction are the weight and the air resistance. The weight of course is acting downwards and the air  resistance is pushing upwards.

Therefore:

W -  AR  = ma                    W = Weight = mg,  AR = Air Resistance = 150.
                                           g = 10 m/s2
mg  - AR  = ma

60(10) - 150 = 60a
600  -  150   = 60a
450 = 60a
60a = 450
a = 450/60
a = 7.5 m/s2

Cheers.