Answer:
56 kg
Explanation:
The change in potential energy of the man is given by:

where
m is the man's mass
g is the gravitational acceleration
is the change in height of the man
In this problem, we have:
is the gain in potential energy
g = 9.8 m/s^2 is the gravitational acceleration
is the change in height
Re-arranging the equation and substituting the numbers, we find the mass:

B!
This is because gravitational pull energy needs a height. The higher the height the higher the energy.
Answer:
This is what they said in english if everyone was wondering
Explanation:
determine the value of the velocity carried by a body whose mass is 3kg and its kinetic energy is 400Joule
Answer:
Unclear without more information
Explanation:
This is about transfer of energy. If you assume there is no energy lost to the environment (virtually impossible) - then all of the potential energy at the beginning would be transferred to kinetic energy along the route.
So, assuming that the rollercoaster has a velocity of 0 m/s at point A, then you can calculate the potential energy using: 
At the point D, you would assume that the energy is split between some kinetic energy and some potential energy. So, we could say that the total energy is the sum of these: 
If we assume all energy is transferred (ie. no energy lost to friction/heat etc) then we can equate these two and solve:

However, this answer seems unlikely given the drawing - which implies that there is perhaps more information that is missing??