Answer:
If something is traveling at a constant velocity, then forces are balanced.
Explanation:
If something is traveling at a constant velocity, then the forces must be balanced because a constant velocity is only achieved with balanced forces.
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The wind tunnel speed that must be used to test the car 1 / 5 model of a car that normally runs at 30 mph is 150 mph
Re = u L / ν
Re = Reynold's number
u = Flow speed
L = Characteristic linear dimension
ν = Kinematic viscosity
ν
= 1.516 *
m² / s
ν
= ν
= 1.516 *
m² / s
L
= L
/ 5
u
= 30 mph
Re
= u
L
/ 5 * 1.516 * 
Re
= 30 L
/ 1.516 * 
In tunnel,
Re
= Re
u
L
/ 5 * 1.516 *
= 30 L
/ 5 * 1.516 * 
u
= 30 * 5
u
= 150 mph
Therefore, the wind tunnel speed that must be used to test the car is 150 mph
To know more about Reynold's number
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Honed I don’t know where the question is
Missing part in the text of the problem:
"<span>Water is exposed to infrared radiation of wavelength 3.0×10^−6 m"</span>
First we can calculate the amount of energy needed to raise the temperature of the water, which is given by

where
m=1.8 g is the mass of the water

is the specific heat capacity of the water

is the increase in temperature.
Substituting the data, we find

We know that each photon carries an energy of

where h is the Planck constant and f the frequency of the photon. Using the wavelength, we can find the photon frequency:

So, the energy of a single photon of this frequency is

and the number of photons needed is the total energy needed divided by the energy of a single photon:
<span>I believe the answer is 0.29.</span>