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3 years ago

Why can’t we see microwaves

Physics

1 answer:

motikmotik3 years ago

8 0

Answer:

The human retina can only detect incident light that falls in waves 400 to 720 nanometers long, so we can't see microwave or ultraviolet wavelengths. This also applies to infrared lights which has wavelengths longer than visible and shorter than microwaves, thus being invisible to the human eye.

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Which is a chemical property of iron?

miss Akunina [59]

I think its A as in density

8 0

3 years ago

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Suppose a plane accelerates from rest for 30 s, achieving a takeoff speed of 80 m/s after traveling a distance of 1200 m down th

vladimir2022 [97]

Answer:

The distance is 300 m.

Explanation:

Given that,

Time = 30 s

Speed = 80 m/s

Distance = 1200 m

Speed of smaller plane = 40 m/s

We need to calculate the acceleration

Using equation of motion

$s= ut+\dfrac{1}{2}at62$

Put the value in the equation

$1200=0+\dfrac{1}{2}\times a\times(30)^2$

$a=\dfrac{2\times1200}{30\times30}$

$a=2.67\ m/s^2$

We need to calculate the distance

Using equation of motion

$v^2=u^2+2as$

Put the value in the equation

$40^2=0+2\times2.67\times s$

$s=\dfrac{40^2}{2\times2.67}$

$s=299.62\approx 300\ m$

Hence, The distance is 300 m.

3 0

2 years ago

radar wave is transmitted and later reflected off an aircraft and recieved 1.4×10^3 sec after being sent out. how far is the air

lutik1710 [3]

I think there's a typo because the answer I'm getting is very large.

This is what I'm getting

--------------------------------------

c = speed of light

c = 3.0 x 10^8 m/sec approximately

This is roughly 300 million meters per second

The time it takes the signal to reach the aircraft and come back is 1.4 x 10^3 seconds. Half of this time period is going one direction (say from the radar station to the aircraft), so (1.4 x 10^3)/2 = 7.0 x 10^2 seconds is spent going in this one direction.

distance = rate*time

d = r*t

d = (3.0 x 10^8) * (7.0 x 10^2)

d = (3.0*7.0) x (10^8*10^2)

d = 21.0 x 10^(8+2)

d = 21.0 x 10^10

d = (2.1 x 10^1) * 10^10

d = 2.1 x (10^1*10^10)

d = 2.1 x 10^11 meters

d = 210,000,000,000 meters (this is 210 billion meters; equivalent to roughly 130,487,950 miles)

3 0

3 years ago

How is the mass number calculated for an element?

natali 33 [55]

<span># of protons + # of neutrons = atomic mass</span>

8 0

3 years ago

Assume that block A which has a mass of 30 kg is being pushed to the left with a force of 75 N along a frictionless surface. Wha

Veronika [31]

Answer:

The force of friction acting on block B is approximately 26.7N. Note: this result does not match any value from your multiple choice list. Please see comment at the end of this answer.

Explanation:

The acting force F=75N pushes block A into acceleration to the left. Through a kinetic friction force, block B also accelerates to the left, however, the maximum of the friction force (which is unknown) makes block B accelerate by 0.5 m/s^2 slower than the block A, hence appearing it to accelerate with 0.5 m/s^2 to the right relative to the block A.

To solve this problem, start with setting up the net force equations for both block A and B:

$F_{Anet} = m_A\cdot a_A = F - F_{fr}\\F_{Bnet} = m_B\cdot a_B = F_{fr}$

where forces acting to the left are positive and those acting to the right are negative. The friction force F_fr in the first equation is due to A acting on B and in the second equation due to B acting on A. They are opposite in direction but have the same magnitude (Newton's third law). We also know that B accelerates 0.5 slower than A:

$a_B = a_A-0.5 \frac{m}{s^2}$

Now we can solve the system of 3 equations for a_A, a_B and finally for F_fr:

$30kg\cdot a_A = 75N - F_{fr}\\24kg\cdot a_B = F_{fr}\\a_B= a_A-0.5 \frac{m}{s^2}\\\implies \\a_A=\frac{87}{54}\frac{m}{s^2},\,\,\,a_B=\frac{10}{9}\frac{m}{s^2}\\F_{fr} = 24kg \cdot \frac{10}{9}\frac{m}{s^2}=\frac{80}{3}kg\frac{m}{s^2}\approx 26.7N$

The force of friction acting on block B is approximately 26.7N.

This answer has been verified by multiple people and is correct for the provided values in your question. I recommend double-checking the text of your question for any typos and letting us know in the comments section.

6 0

3 years ago

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