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At some instant and location, the electric field associated with an electromagnetic wave in vacuum has the strength 98.5 V/m. Fi

77julia77 [94]

Answer:

$B = 3.28 \times 10^{-7} T$

$u_{density} = 4.3 \times 10^{-8} J/m^3$

$Intensity = 12.88 W/m^2$

Explanation:

As we know that the electric field strength in vacuum due to electromagnetic waves is given as

$E = 98.5 V/m$

now we know the relation between electric field and magnetic field as

$B = \frac{E}{c}$

$B = \frac{98.5}{3\times 10^8}$

$B = 3.28 \times 10^{-7} T$

For energy density we know that

$u_{density} = \frac{1}{2}\epsilon_0 E^2$

$u_{density} = \frac{1}{2}(8.85 \times 10^{-12})(98.5)^2$

$u_{density} = 4.3 \times 10^{-8} J/m^3$

Power flow per unit area is given as

$Intensity = energy density \times speed$

$Intensity = (4.3 \times 10^{-8})(3\times 10^8)$

$Intensity = 12.88 W/m^2$

5 0

3 years ago

Two fish swimming in a river have the following equations of motion:

IRINA_888 [86]

Answer:

The second fish, X2, is moving faster than the first fish, X1

Explanation:

The given parameters for the equation of motion of the fishes are;

X1 = -6.4 m + (-1.2 m/s)×t

X2 = 1.3 m + (-2.7 m/s)×t

The given equation are straight line equations in the slope and intercept form, where the slope is the speed and in m/s and the intercept is the starting point of swimming of the fishes

For the first fish, the intercept = -6.4 m, the slope = the speed = -1.2 m/s

For the second fish, the intercept = 1.3 m, the slope = the speed = -2.7 m/s

Whereby the fishes are swimming in the opposite direction of the measurement of length, we have;

The magnitude of the speed of the second fish $\left | -2.7 \ m/s \right | = 2.7 \ m/s$ , is larger than the magnitude of the speed of the first fish $\left | -1.2 \ m/s \right | = 1.2 \ m/s$

Therefore, the second fish, X2, is moving faster than the first fish, X1.

8 0

3 years ago

A 2800 kg truck moving at 12 m/s to the right hits a stopped 1100 kg car. What is the combined velocity the moment they stick to

leva [86]

Answer:

The combined velocity is 8.61 m/s.

Explanation:

Given that,

The mass of a truck, m = 2800 kg

Initial speed of truck, u = 12 m/s

The mass of a car, m' = 1100 kg

Initial speed of the car, u' = 0

We need to find the combined velocity the moment they stick together. Let it is V. Using the conservation of momentum.

$m_1v_1+m_2v_2=(m_1+m_2)V\\\\V=\dfrac{m_1v_1+m_2v_2}{(m_1+m_2)}\\\\V=\dfrac{2800\times 12+0}{2800+1100}\\\\V=8.61\ m/s$

So, the combined velocity is 8.61 m/s.

5 0

3 years ago

How high does a rocket have to go above Earth's surface before its weight is half of what it is on Earth?

Contact [7]

Answer:

$h=1.6\times 10^6\ m$

Explanation:

As we know that the acceleration due to gravity decreases with height.

At certain height it will get to the half of its value on the surface of the earth.

As we know that the weight on the surface of the earth is given as:

$w=m.g$

where:

m = mass of the object

g = acceleration due to gravity of the substance

Since mass of the substance is constant so the variation is weight is possible only due to change in the acceleration due to gravity.

<u>We know that the variation of the acceleration due gravity with height is given as:</u>

$g_{_h}=g\times (1-\frac{2h}{R} )$

where:

$g_{_h}=$ value to acceleration due to gravity at height h

g = acceleration due to gravity at the earth's surface

h = height of the object

R = radius of the earth = $6400\ km$

according to question the weight becomes half, so,:

$4.9=9.8\times (1-\frac{2h}{6400\times10^3} )$

$h=1.6\times 10^6\ m$ is the height a rocket has to go above Earth's surface before its weight is half of what it is on Earth.

4 0

3 years ago

These UV photons can break chemical bonds in your skin to cause sunburn—a form of radiation damage. If the 305 nm radiation prov

astraxan [27]

Answer:

energy = 391.902 kJ /mol

Explanation:

given data

wavelength = 305 nm = 305 × $10^{-9}$ m

to find out

average energy

solution

we know speed of light is 3 × $10^{8}$ m/s

so we find frequency here first by speed of light formyla

speed = wavelength × frequency

3 × $10^{8}$ = 305 × $10^{-9}$ × frequency

frequency = 9.8360 × $10^{14}$ $s^{-1}$

so energy is

energy = hf

here h = 6.62 × $10^{-34}$ J-s

so

energy = 6.62 × $10^{-34}$ × 9.8360 × $10^{14}$

energy = 6.51 × $10^{-14}$ J

so

energy = 6.51 × $10^{-14}$ × $\frac{6.02*10^23}{1000}$ kJ/mol

energy = 391.902 kJ /mol

7 0

4 years ago