Answer:
Planting of trees on sloped surfaces is a method of conservation that utilizes the roots of plants. Planting trees on such areas would prevent hazards and maintain the soil formation future since the roots would hold the soil together preventing or minimizing any soil erosion.
Answer:

Explanation:
Btu of British thermal unit is a unit of heat. The relation between btu/year and watts is given by :

So,
is equal to 11 kW. Hence, the correct option is (d).
Answer:
The value is 
Explanation:
From the question we are told that
The mass of each sphere is 
The length of the string is
The angle of with the vertical is 
The acceleration due to gravity is 
Generally the force acting between the forces is mathematically represented as

=> 
Generally from Pythagoras theorem the radius of the circular curve created by the force is

=> 
=>
=> 
=> 
=> 