Coal is the answer to the question
Answer:
The height is 
Explanation:
From the question we are told that
The combined mass of the child and the sled is 
The speed of the sled is 
Generally applying SOHCAHTOA on the slope which the combined mass is down from
Here the length of the slope(L) where the combined mass slides through is the hypotenuses
while the height(h) of the height of the slope is the opposite
Hence from SOHCAHTOA

=> 
Generally from the kinematic equation we have that

Here the u is the initial velocity of the combined mass which is zero since it started from rest
and a is the acceleration of the combined mass which is mathematically evaluated as


=> 
=> 
=> 
=> 
Wind power is produced from the
wind turbines or sails that uses air flow to convert it into mechanical power.
It is an alternative to fossil fuel burning, it is all around, renewable,
clean, produces no greenhouse gases and uses little land. The advantages of
wind power have been greatly praised by many. However, it has disadvantages.
Wind power especially at farm is noisy and may spoil the view for their
neighboring people. Also the amount of electricity depends on the strength of
the wind. If no wind is around, no electricity is produced.