Under the influence of a gravitational field, any falling object
will undergo acceleration.
Therefore, option one and two is obviously out. If something
undergo acceleration, it cannot have a constant velocity.
The gravitational field strength of planet Earth is approximately
10N/kg (memorise). Therefore, using the derived formulae from the
Newton's Second Law, 'F=ma', where F is the weight of the object
(W=mg=10*2.5) (since weight is the only force acting on the object,
ignoring the effect of air resistance obviously), we get a=F/m=
(10*2.5)/2.5=10m/s^2.
