it’s actually 7th grade science no physics pls answer it’s a lot of points

What do the historical communication technologies in these photos have in common?
(pictures are shown below)

The height of the cliff, given that her phone landed 20 m away when she accidentally threw her phone with a velocity of 5 m/s is 78.4 m

To determine the height of the cliff, we must first obtain the time taken for her phone to reach the ground. This is obtained as follow:

s = ut

20 = 5 × t

Divide both sides by 5

t = 20 / 5

t = 4 s

Finally, we shall determine the height of the cliff. Details below:

h = ½gt²

h = ½ × 9.8 × 4²

h = 4.9 × 16

h = 78.4 m

Thus, the height of the cliff is 78.4 m

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The force that must be exerted on the master cylinder of the hydraulic lift to support the weight of car is  147.2 N .

The Pascal's Law states that the relation between the pressure , force and area is given as :

Pressure = Force/Area ;

given that the diameter of the master cylinder is = 1.93 cm ;

so radius of master cylinder = 1.93/2 = 0.965 cm = 0.00965 m ;

the diameter of slave cylinder is = 24.9 cm ;

the radius of the slave cylinder = 24.9/2 = 12.45 m = 0.1245 m ;

Area of slave cylinder (A₁)= π(0.1245)² = 0.0486 m²

Area of the master cylinder (A₂) =  π(0.00965)² = 0.000292 m² ;

given mass of the car = 2500 Kg ,

the force exerted will be : F = m*a

F₁ = 2500*9.8 = 24500 N ;

F₁/A₁ = F₂/A₂

So , 24500/0.0486 = F₂/0.000292

F₂ = (24500/0.0486)×0.000292

F₂ = 147.2 N

Therefore , the force exerted on the master cylinder is 147.2 N  .

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The Effective Spring Constant is [tex](\frac{k1k2}{k1 + k2} )[/tex] for a system of 2 springs with spring constant k1 and k2.

The term "spring constant" refers to the proportional constant k. It gauges the stiffness of the spring. A spring exerts a force F = -kx in the direction of its equilibrium position when it is stretched or compressed to a length that differs by an amount x from its equilibrium length.

Spring constants are available in plural (physics) a quality of a spring that is determined by the force acting on the spring to the displacement it produces.

K stands for the proportionality constant, commonly referred to as the "spring constant." In layman's words, stiffness and strength are shown by the k variable in Hooke's law (F = -kx). An item requires more force to be stretched to a specific length the greater the value of k.

Let the force actiong be F N

then , if k1 is the spring constant of spring 1

F = x1 * k1

or, x1 = F/k1.

Similarly for spring 2

x2 = F/k2

Now x1 + x2 = F (1/k1 + 1/k2)

or effective displacement

X= [tex]F(\frac{1}{k1} + \frac{1}{k2} )[/tex]

or, F = [tex]X * (\frac{k1k2}{k1 + k2} )[/tex]

So the Effective Spring Constant is [tex](\frac{k1k2}{k1 + k2} )[/tex].

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Newton's third law states that any action will have a(n) equal and opposite reaction.

The free-fall acceleration on Mars is 3.71 m/s²

Given :

gravitational force acting on the robot is 504.6 N

F= 504.6 N

mass of the robot  = 136 kg

a = F/ m

= 504.6/ 136 =3.71 m/s²

The free-fall acceleration on Mars is 3.71 m/s²

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When it happens mother should have to do cool the burn with tap water for 10 to 20 minutes immediately.

Stop the burning process. Cool the burn. Supply pain relief.

Before the arrival of qualified emergency help, you should:

Pain and skin injury from wet heat or vapors can result from hot water scalding. Because the damaged tissues and cells are destroyed, this kind of burn can be deadly. The heat could even cause your body to go into shock. These burns can be fatal in more severe circumstances.

Cool the burn.

Place the affected area under cool (not cold) flowing water for about 10 minutes. Until the pain goes away, apply a cool, wet cloth to the burned area of the face. If you have a mouth burn from hot food or drink, place a piece of ice in your mouth for a while.

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Recommend frequent hand washing are the treatment method developed after the discovery of germ theory.

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True. The Big Bang Theory is the current scientific explanation for the origin and evolution of the universe. According to this theory, the universe was initially in a state of extremely high density and temperature, and it has been expanding and cooling since its inception.

One reason we cannot directly observe the Big Bang is that the universe's density was so low at that time that there were no solid particles, such as atoms or molecules, that could have formed into stars or galaxies. Instead, the universe was filled with a hot, ionized plasma that was too diffuse to be observed by telescopes. Another reason is that the expansion of the universe has caused the light and other electromagnetic radiation that was emitted during the Big Bang to become redshifted, or stretched out in wavelength, over time. This means that the light from the earliest moments of the universe has shifted into the microwave and radio frequency ranges, which are not visible to the human eye. Therefore, while we can infer some details about the conditions of the early universe based on observations of the cosmic microwave background radiation and the large-scale structure of the universe, we cannot directly observe the Big Bang itself.

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The velocity of vehicles after the collision is 15.82m/sec if car mass is 1.4 × 10³kg and truck mass is 2×10³kg

We know that we need to conserve the momentum of watermelon in a certain direction. Also,we know that initial momentum of watermelon is zero,it means that according to law of conservation of momentum final momentum should be zero.

We know that momentum =mass × velocity

So,initial momentum of car is =1.4 × 10³kg × 37km/hr

Similarly,,initial momentum of truck=2×10³kg × 35km/hr

Now,it is given that both vehicles lock together,so total mass of both vehicles is =1.4 × 10³kg +  2×10³kg=3.4 ×10³kg

Assume final velocity of both vehicle is v

So,following the law of conservation,we get

=>1.4 × 10³kg × 37 + 2×10³kg × 35 = 3.4 ×10³ ×v

=>51.8 ×10³ + 2×10³=3.4×10³ ×v

=>53.8 ×10³ kg-m/sec = 3.4×10³ ×v

=>v = 53.8/3.4

=>v=15.82m/sec

Hence,final velocity of both vehicle after collision is 15.82m/sec.

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The speed of the wave is determined as 18 m/s.

option D is the correct answer.

The speed of the wave is the rate of change of wave's displacement with time.

The speed of the wave is calculated by applying the formula relating speed, wavelength and frequency of the wave as shown below.

v = fλ

where;

The frequency of the wave is calculated as follows;

f = 1 / T

where;

The period of a wave is the time taken for the wave to complete one cycle.

In the picture given, 3 cycles of the wave = 0.5 s

1 cycle of the wave = ?

= 0.5 s / 3

= 0.16667 s

f = 1 / T

f = 1 / 0.16667

f = 6 Hz

The speed of the wave is calculated as follows;

v = fλ

v = 6 Hz  x  3 m

v = 18 m/s

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parallel processing perceiving the color, motion, and form of a bird in flight illustrates.

Option a is correct.

According to the trichromatic theory, our ability to perceive red, green, and blue hues as well as how they affect our cerebral activity are both explained by cones (Like a projection T.V.). Consequently, the precise colour we see is determined by the proportion of each colour to the others.

The three kinds of cone receptors that are responsible for colour vision are the foundation of the trichromatic hypothesis of colour vision. Beginning in the 18th century, this hypothesis has a very long history.

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An average tendon can withstand 16000 per square inch of force (psi). The Achilles tendon may begin to fail at a force of F = 1280 pounds.

That meaning of the term "force" is obvious. At this point, it is quite acceptable to refer to a force as a push or possibly a pull. An item does not "have energy in it" or "encompass energy." A force is applied to one thing by another. A factor is anything that affects non-living things as well.

Inertia is what holds the cosmos together. Literally. That could prevent matter from having the electric forces necessary to produce its system layout. Vibrating particles generate heat and rotational motion, which operate to counteract inertia.

Area of tendon 0.4×0.2

=0.08 square inch.

0.08 square inch tendon =16000×0.08

F =1280 pound.

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When a soap bubble 100 nm thick and illuminated by white light incident perpendicular to its surface, then wavelength, λ is calculated =  5.32 *10^-7 m.

The ratio of the speed of light in a vacuum, c, to the speed of light in a medium, c' is called as index of refraction. One of the consequence of this difference in speed is that when light goes from one medium to another at an angle, then the propagation vector in the new medium has a different angle with respect to normal.

Given, t= 100nm= 100 * 10 ^-9  n= 1.33

ΔФ1 = λ/4

ΔФ2 = 2√2 t λ n/2 λ

=2 t n

=2 * 100 * 10 ^-9 * 1.33

= 2.66 *10^-7

2.66 *10^-7= λ/2

λ=  5.32 *10^-7 m.

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