Answer:
mechanical advantage!
Explanation:
The Mechanical advantage of a machine is the factor by which the machine changes the input force.
When a a machine multiplies an input force, that's called a mechanical advantage.
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Defenition of Mechanical Advantage
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For Blake:
3 boxes at a distance of 10 meters each, each box weighs 20 N
Work done by Blake = 3 * 10m * 20N
= 600 J
Power = 600 J/ 2 min
= 300 J/min
For Sandra:
4 boxes, 15 N each at a distance of 12 meters each.
Work done by Sandra = 4 * 15 N *12m
= 720 J
Power = 720 J/ 4 min
= 180 J/min
Blake does less work than Sandra.
Blake's power is more than Sandra's.
Energy of the waves are redistributed to form a resultant wave with amplitude given by the summation of individual wave's amplitude.
<span>If the two waves are of same frequency, speed and amplitude and travelling in opposite direction den stationary waves are form.</span>
The refractive index of water is

. This means that the speed of the light in the water is:

The relationship between frequency f and wavelength

of a wave is given by:

where v is the speed of the wave in the medium. The frequency of the light does not change when it moves from one medium to the other one, so we can compute the ratio between the wavelength of the light in water

to that in air

as

where v is the speed of light in water and c is the speed of light in air. Re-arranging this formula and by using

, we find

which is the wavelength of light in water.
To solve this problem we will use the heat transfer equations, to determine the amount of heat added to the body. Subsequently, through the energy ratio given by Plank, we will calculate the energy of each of the photons. The relationship between total energy and unit energy will allow us to determine the number of photons
The mass of water in the soup is 477g
The change in temperate is

Use the following equation to calculate the heat required to raise the temperature:

Here,
m = Mass
c = Specific Heat


The wavelength of the ration used for heating is 
The number of photons required is the rate between the total energy and the energy of each proton, then

This energy of the photon is given by the Planck's equation which say:

Here,
h = Plank's Constant
c = Velocity of light
Wavelength
Replacing,


Now replacing we have,


Therefore the number of photons required for heating is 