let the distance of pillar is "r" from one end of the slab
So here net torque must be balance with respect to pillar to be in balanced state
So here we will have

here we know that
mg = 19600 N
Mg = 400,000 N
L = 20 m
from above equation we have



so pillar is at distance 10.098 m from one end of the slab
Water equal to iron is greater than cooper
Answer:
Explanation:
a ) Direction of the magnetic field will be in positive x direction.
The direction of the vector E X B gives the direction of motion of wave.
b ) Magnitude of magnetic field is given by the relation
E₀ / B₀ = c , c is velocity of light
B₀ = E₀ / c
= 20 / (3 x 10⁸)
= 6.67 x 10⁻⁸ T
c ) Average power flowing per unit area by this wave is called Poynting vector
c ε₀E₀² , ε₀ = 8.85X10⁻¹²
= 3 X 10⁸ X 8.85 X 10⁻¹² X 20²
= 1.062 W m⁻²