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3 years ago

To a nighttime observer on Earth, how many degrees do the stars appear to move around Polaris in 3 hours?

1 answer:

5 0

The correct answer is 45 degrees. 360 degrees is 24 hours, because it takes a whole day for the earth to turn in one whole circle. So, to find how many degrees the stars seem to move per hour, simply divide the total number of degrees by the total number of hours in a day: 360/24 = 15. Since the question is asking how much the stars appear to move in 3 hours, now multiply the number of degrees per hour times 3: 15 x 3 = 45.

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An inverse-time circuit breaker (CB) is used for branch-circuit short-circuit and ground-fault protection for a 30-horsepower, 2

Maru [420]

Answer:

Explanation:

Motor rating is given in horsepower (hp), it will be converted in watt (W).

Standard to install circuit breaker for an electric circuit is usually 20% ~ 25% more than the Rated Current of the circuit

while

Standard to install overload relay for an electric circuit is usually 20% ~ 25% more than the Running Current of the circuit.

So, to find the maximum capacity of the circuit breaker, rated current of the motor will be multiplied by 1.2 ~ 1.25

Step by Step Explanation:

30hp = 22371W (as 1hp = 745.7)

Assuming unity power factor (cosФ=1) and 208V phase to phase voltage:

Rated Power (watt) = √3 . V.I. cosФ

{if 208V is phase to neutral voltage, then use following formula:

Rated Power (watt) = 3 . V.I. cosФ}

$\frac{22371}{\sqrt{3} * 208 * 1} = I$

Rated Current = 62.169A

So, required maximum rating for circuit breaker is:

20% to 25% of the rated current = 62.17*1.2 ~ 62.17*1.25

=74.6A ~ 77.7A

Hence, any breaker between the above mentioned rating will be appropriate.

3 0

2 years ago

Why is the gravitational potential energy of an object 1 meter above Earth's surface more than its potential energy 1 meter abov

Umnica [9.8K]

I Believe The Answer Is C

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2 years ago

A steel cable has a cross-sectional area 4.49 × 10^-3 m^2 and is kept under a tension of 2.96 × 10^4 N. The density of steel is

Lemur [1.5K]

Answer:

The transverse wave will travel with a speed of 25.5 m/s along the cable.

Explanation:

let T = 2.96×10^4 N be the tension in in the steel cable, ρ = 7860 kg/m^3 is the density of the steel and A = 4.49×10^-3 m^2 be the cross-sectional area of the cable.

then, if V is the volume of the cable:

ρ = m/V

m = ρ×V

but V = A×L , where L is the length of the cable.

m = ρ×(A×L)

m/L = ρ×A

then the speed of the wave in the cable is given by:

v = √(T×L/m)

= √(T/A×ρ)

= √[2.96×10^4/(4.49×10^-3×7860)]

= 25.5 m/s

Therefore, the transverse wave will travel with a speed of 25.5 m/s along the cable.

7 0

3 years ago

Gli iceberg nel Nord Atlantico rappresentano un rischio per la navigazione, costringendo ad allungare le rotte di navigazione di

nikklg [1K]

I DONT UNDERSTND IS ANOTHER LANGUAGR

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3 years ago

A)A certain medical machine emits x-rays with a minimum wavelength of 0.024 nm. One day, the machine has an electrical problem a

oee [108]

Answer:

(a) 0.032 nm

(b) 39,235 eV

Explanation:

(a) The energy of a photon can be calculated using:

E = hc/λ equation (1)

where:

h = 4.13*10^-15 eV.s

c = 3*10^8 m/s

λ = 0.024*10^-9 m

Thus:

E = (4.13*10^-15)*(3*10^8)/0.024*10^-9 = 51,625 eV

Then we calculate 76% of this estimated energy and determine the new wavelength:

$E_{new} = 0.76*51625 = 39,235 eV$

Using equation (1) to determine the new wavelength:

λ $_{new} = \frac{h*c}{E_{new} }$

λ $_{new}$ = (4.13*10^-15)*(3*10^8)/39235 = 3.15*10^-11 m = 0.032 nm

(b) As calculated in part (a), the maximum x-ray energy this machine can produce is $E_{new} = 0.76*51625 = 39,235 eV$

$E_{ka} = (10.2 eV)*(Z-1)^{2}$

where Z is the atomic number = 84.

$E_{ka} = (10.2 eV)*(84-1)^{2}$ = 70,267.8 eV

4 0

2 years ago