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2 years ago

Q7 Describe two types of atomic change that produce electromagnetic waves.

1 answer:

Crank2 years ago

7 0

When a neutron or a proton in the nucleus changes a gamma ray is produced (gamma rays are electromagnetic waves)

When an electron drops from a higher energy level to a lower energy level an electromagnetic wave is give off.

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1. What are the 3 spheres of Earth?

dolphi86 [110]

they are the lithosphere (land), hydrosphere (water), biosphere (living things), and atmosphere (air).

8 0

2 years ago

A long copper rod of diameter 2.0 cm is initially at a uniform temperature of 100°C. It is now exposed to an air stream at 20°C

Lisa [10]

Answer:

t = 4.0 min

Explanation:

given data:

diameter of rod = 2 cm

T_1 = 100 degree celcius

Air stream temperature = 20 degree celcius

heat transfer coefficient = 200 W/m2. K

WE KNOW THAT

copper thermal conductivity = k = 401 W/m °C

copper specific heat Cp = 385 J/kg.°C

density of copper = 8933 kg/m3

charateristic length is given as Lc

$Lc = \frac{V}{A_s}$

$Lc = \frac{\frac{\pi D^2}{4} L}{\pi DL}$

$Lc = \frac{D}{4}$

$Lc = \frac{0.02}{6} = 0.005 m$

Biot number is given as $Bi = \frac{hLc}{k}$

$Bi = \frac{200*0.005}{401}$

Bi = 0.0025

As Bi is greater than 0.1 therefore lumped system analysis is applicable

so we have

$\frac{T(t) - T_∞}{Ti - T_∞} = e^{-bt}$ ............1

where b is given as

$b = \frac{ hA}{\rho Cp V}$

$b = \frac{ h}{\rho Cp Lc}$

$b = \frac{200}{8933*385*0.005}$

b = 0.01163 s^{-1}

putting value in equation 1

$\frac{25-20}{100-20} = e^{-0.01163t}$

solving for t we get

t = 4.0 min

6 0

3 years ago

is it true that the composition of the atmosphere changes every few kilometers as you move away from earth

laiz [17]

Yes,it's true ok? So how have you been doing

5 0

3 years ago

An engine moves a motorboat through water at a constant velocity of 22 meters/second. If the force exerted by the motor on the b

trapecia [35]

Answer: Option B: 1.3×10⁵ W

Explanation:

$Power = \frac{Work \hspace{1mm} done}{Time}$

$P=\frac{W}{t}$

Work Done, $W= F.s$

Where s is displacement in the direction of force and F is force.

$\Rightarrow P = \frac{F.s}{t} =F \times \frac{s}{t}=F.v$

where, v is the velocity.

It is given that, F = 5.75 × 10³N

v = 22 m/s

P = 5.75 × 10³N×22 m/s = 126.5 × 10³ W ≈1.3×10⁵W

Thus, the correct option is B

6 0

2 years ago

Which type of map would you most likely use to locate mineral deposits? A. topographic B. geologic C. satellite D. hazard

qwelly [4]

I think you would be using a topographic Map, So the answer should be A

3 0

2 years ago