Answer:
The intensity of the EM wave is 5.729 W/m²
The rms value of the electric field is 46.452 V/m
Explanation:
Given;
power of the electromagnetic wave, P = 1800 W
The intensity of light is given by;
I = P / A
Where;
A is the surface area of the sphere = 4πr²
A is the surface area of the sphere = 4π(5)²
A is the surface area of the sphere = 314.2 m²
The intensity is calculated as;
I = P / A
I = (1800) / (314.2)
I = 5.729 W/m²
The rms value of the electric field is given by;
Answer:
f = 347.08 N
Explanation:
The frictional force exerted by the floor on the refrigerator is given as follows:
where,
f = frictional force = ?
μ = coefficient of static friction = 0.58
W = Weight of refrigerator = mg
m = mass of refrigerator = 61 kg
g = acceleration due to gravity = 9.81 m/s²
Therefore,
<u>f = 347.08 N</u>
Answer:
<em>Correct choice: b 4H</em>
Explanation:
<u>Conservation of the mechanical energy</u>
The mechanical energy is the sum of the gravitational potential energy GPE (U) and the kinetic energy KE (K):
E = U + K
The GPE is calculated as:
U = mgh
And the kinetic energy is:
Where:
m = mass of the object
g = gravitational acceleration
h = height of the object
v = speed at which the object moves
When the snowball is dropped from a height H, it has zero speed and therefore zero kinetic energy, thus the mechanical energy is:
When the snowball reaches the ground, the height is zero and the GPE is also zero, thus the mechanical energy is:
Since the energy is conserved, U1=U2
For the speed to be double, we need to drop the snowball from a height H', and:
Operating:
Dividing [2] by [1]
Simplifying:
Thus:
H' = 4H
Correct choice: b 4H