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4 years ago

How does light travel??????????

Physics

1 answer:

adell [148]4 years ago

6 0

Light travels through waves.

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Figure shows three blocks that are being pulled along a smooth horizontal surface. The masses of the blocks

Eva8 [605]

Answer:

The pulling force F is 200 N

Explanation:

We note that the tension in a rope between two or three blocks is given by the relation;

Where we have;

m₁ → T₁ → m₂ → T₂ → m₃ → F

$T_1 = \dfrac{m_1}{m_1 + m_2 + m_3} \times F$

$T_2 = \dfrac{m_1 + m_2}{m_1 + m_2 + m_3} \times F$

m₁ = 2 kg

m₂ = 4 kg

m₃ = 4 kg

T₂ = 120 N

Therefore, by substitution, gives;

2 kg → T₁ → 4 kg → 120 N → 4 kg → F

$120 \ N = \dfrac{2 \ kg + 4 \ kg}{2 \ kg+ 4 \ kg+ 4 \ kg} \times F = \dfrac{6 \ kg}{10 \ kg} \times F$

F = 120 N × (10 kg)/(6 kg) = 200 N

The pulling force F = 200 N.

7 0

3 years ago

An electric air heater consists of a horizontal array of thin metal strips that are each 10 mm long in the direction of an airst

sweet-ann [11.9K]

Answer:

see explanation below

Explanation:

Given that,

$T_1 =$ 500°C

$T_2$ = 25°C

d = 0.2m

L = 10mm = 0.01m

U₀ = 2m/s

Calculate average temperature

$\\T_{avg} = \frac{T_1 + T_2}{2} \\\\T_{avg} = \frac{500 + 25}{2} \\\\T_{avg} = 262.5$

262.5 + 273

= 535.5K

From properties of air table A-4 corresponding to $T_{avg}$ = 535.5K $\approx 550K$

k = 43.9 × 10⁻³W/m.k

v = 47.57 × 10⁻⁶ m²/s

$P_r = 0.63$

Number for the first strips is equal to

$R_e_x = \frac{u_o.L}{v}$

$R_e_x = \frac{2\times 0.01}{47.57 \times 10^-^6 }\\\\= 420.4$

Calculating heat transfer coefficient from the first strip

$h_1 = \frac{k}{L} \times 0.664 \times R_e_x^1^/^2 \times P_r^1^/^3$

$h_1 = \frac{43.9 \times 10^-^3}{0.01} \times 0.664\times420 \times 4^1^/^2 \times 0.683^1^/^3\\\\= 52.6W/km^2$

The rate of convection heat transfer from the first strip is

$q_1 = h_1\times(L\times d)\times(T_1 - T_2)\\\\q_1 = 52.6 \times (0.01\times0.2)\times(500-25)\\\\q_1 = 50W$

The rate of convection heat transfer from the fifth trip is equal to

$q_5 = (5 \times h_o_-_5-4\times h_o_-_4) \times(L\times d)\times (T_1 -T_2)$

$h_o_-_5 = \frac{k}{5L} \times 0.664 \times (\frac{u_o\times 5L}{v} )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.05} \times0.664\times (\frac{2 \times 0.05}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 25.5W/Km^2$

Calculating $h_o_-_4$

$h_o_-_4 = \frac{k}{4L} \times 0.664 \times (\frac{u_o\times 4L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.04} \times0.664\times (\frac{2 \times 0.04}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 26.3W/Km^2$

The rate of convection heat transfer from the tenth strip is

$q_1_0 = (10 \times h_o_-_1_0-9\times h_o_-_9) \times(L\times d)\times (T_1 -T_2)$

$h_o_-_1_0 = \frac{k}{10L} \times 0.664 \times (\frac{u_o\times 10L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.1} \times0.664\times (\frac{2 \times 0.1}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 16.6W/Km^2$

Calculating

$h_o_-_9 = \frac{k}{9L} \times 0.664 \times (\frac{u_o\times 9L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.09} \times0.664\times (\frac{2 \times 0.09}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 17.5W/Km^2$

Calculating the rate of convection heat transfer from the tenth strip

$q_1_0 = (10 \times h_o_-_1_0-9\times h_o_-_9) \times(L\times d)\times (T_1 -T_2)\\\\q_1_0 = (10 \times 16.6 -9\times 17.5) \times(0.01\times 0.2)\times (500 -25)\\\\=8.1W$

The rate of convection heat transfer from 25th strip is equal to

$q_2_5 = (25 \times h_o_-_2_5-24\times h_o_-_2_4) \times(L\times d)\times (T_1 -T_2)$

Calculating $h_o_-_2_5$

$h_o_-_2_5 = \frac{k}{25L} \times 0.664 \times (\frac{u_o\times 25L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.25} \times0.664\times (\frac{2 \times 0.25}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 10.5W/Km^2$

Calculating $h_o_-_2_4$

$h_o_-_2_4 = \frac{k}{24L} \times 0.664 \times (\frac{u_o\times 24L}{v } )^1^/^2\times Pr^1^/^3\\\\= \frac{43.9\times10^-^3}{0.24} \times0.664\times (\frac{2 \times 0.24}{47.57 \times 10^-^6} )^1^/^2\times 0.683^1^/^3\\\\= 10.7W/Km^2$

Calculating the rate of convection heat transfer from the tenth strip

$q_2_5 = (25 \times h_o_-_2_5-24\times h_o_-_2_4) \times(L\times d)\times (T_1 -T_2)\\\\q_1_0 = (25 \times 10.5 -24\times 10.7) \times(0.01\times 0.2)\times (500 -25)\\\\=5.4W$

6 0

4 years ago

A small boat is moving at a velocity of 3.35m/s when it is accelerated by a river current perpendicular to the initial direction

mr_godi [17]

Answer:

v =7.1 m/s

Explanation:

Given that

u = 3.35 m/s

t= 5 s

a= 0.75 m/s²

The final velocity = v

We know v = u +at

v=final velocity

u=initial velocity

Now by putting the values in the above equation

v = 3.35 + 0.75 x 5 m/s

v =7.1 m/s

Therefore the final velocity will be 7.1 m/s

7 0

3 years ago

The first step in the scientific method is to ___________.

Ann [662]

A. Is the answer definitely

7 0

3 years ago

Read 2 more answers

How much work do you do when you push a 400 kg car for 6 m with a force of 300 N? What is the car’s final speed if all your work

Anit [1.1K]

Answer:

Work=1800 J

Speed=3m/s

Explanation:

Work is product of force and distance moved, expressed as

W=Fd

Where F is force and d is distance in meters

Substituting 300 N for force and 6 m for d then

W=300*6=1800 J

Kinetic energy is given by

KE=½mv²

Where m is the mass and v is velocity

Here, KE=W hence

W=½mv²

Making v the subject then

$v=\frac {2W}{m}$

Substituting 1800J for W and 400 kg for m then

$v=\frac {2*1800}{400}=3m/s$

Therefore, velocity is 3 m/s

4 0

3 years ago