Both equinoxes ... September 21 and March 21.
Formula to find gravitational potential energy:
mgh
m: mass
g: gravitational acceleration
h: height (relative to reference level)
so the P.E. at 1.0.m is (5x9.8x1)= 49J
P.E. at 1.5m is (5x9.8x1.5) =73.5J
P.E. at 2.0m is (5x9.8x2)=98J
I believe this would be an example of Mary's velocity. We have her speed and direction which is all you need to find velocity.
Explanation:
(9) Acceleration due to gravity is defined as the acceleration between two massive bodies when they are moving under free fall.
The relation between g and G is given by :

Where
G is universal gravitational constant
M is mass of the earth
r is distance
(10) The unwanted product that can toxify the crops are called weeds. To control weeds, a chemical called weedicides are sprayed in the field. Some other methods to control them are Ploughing or tilling of soil etc.