Answer:

Explanation:
From the question we are told that:
Crane Length 
Crane Mass 
Arm extension at lifting end 
Arm extension at counter weight end 
Load 
Generally the equation for Torque Balance is mathematically given by



Potential energy behind dams
Answer:
D. 4000 km
Explanation:
f = Frequency of wave that is being transmitted = 76 Hz
= Wavelength of wave that is being transmitted
v = The velocity of electromagnetic waves through air = 
Velocity of a wave is given by

Hence, the approximate wavelength of the waves is 4000 km