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monitta
3 years ago
11

Suppose an astrophotographer hands you a picture with star trails taken looking toward the north celestial pole. If the star tra

ils are 1/6 of a complete circle, about how many hours was the picture exposed? Hint: How many hours would it take the stars to make a full circle? Report your answer to the nearest whole number
Physics
1 answer:
Reil [10]3 years ago
4 0

Answer:

Our answer will be 4 hours.

Explanation:

It takes 24 hours to complete a circle(360° rotation)

Hence to complete 1/6th of complete circle it will take 24/6= 4 hours

Exact in integers= 4 hrs. Hence our answer will be 4 hours.

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A 37-cm-long wire of linear density 18 g/m vibrating at its second mode, excites the third vibrational mode of a tube of length
lora16 [44]

Answer:

T = 4.42 10⁴ N

Explanation:

this is a problem of standing waves, let's start with the open tube, to calculate the wavelength

        λ = 4L / n                 n = 1, 3, 5, ...    (2n-1)

How the third resonance is excited

       m = 3

       L = 192 cm = 1.92 m

       λ = 4 1.92 / 3

       λ = 2.56 m

As in the resonant processes, the frequency is maintained until you look for the frequency in this tube, with the speed ratio

      v = λ f

      f = v / λ

      f = 343 / 2.56

      f = 133.98 Hz

       

Now he works with the rope, which oscillates in its second mode m = 2 and has a length of L = 37 cm = 0.37 m

The expression for standing waves on a string is

           λ = 2L / n

           λ = 2 0.37 / 2

           λ = 0.37 m

The speed of the wave is

          v = λ f

As we have some resonance processes between the string and the tube the frequency is the same

          v = 0.37 133.98

          v = 49.57 m / s

Let's use the relationship of the speed of the wave with the properties of the string

              v = √ T /μ

              T = v² μ

              T = 49.57²   18

              T = 4.42 10⁴ N

4 0
3 years ago
Read 2 more answers
A person exerts a tangential force of 37.7 N on the rim of a disk-shaped merry-go-round of radius 2.75 m and mass 144 kg. If the
Shkiper50 [21]

Answer:

 ω = 0.467 rad/s

Explanation:

given,

tangential force exerted by the person = 37.7 N

radius of merry-go-round = 2.75 m

mass of merry-go-round  = 144 Kg

angle =  33.2°

moment of inertia

I = \dfrac{1}{2} m R^2

I = \dfrac{1}{2}\times 144 \times 2.75^2

    I = 544.5 kg.m²

torque = force  x radius

τ = 37.7 x  2.75

τ = 103.675 N.m

angular acceleration

\alpha= \dfrac{\tau}{I}

\alpha= \dfrac{103.675}{544.5}

 α = 0.190 rad/s²

now ,

distance = 33.2\times \dfrca{2\pi}{360}

d = 0.579 rad

we know,

using equation of rotational motion

d = \omega t + \dfrac{1}{2}\alpha t^2

0.579 = \dfrac{1}{2}\times 0.190\times t^2

 t = 2.46 s

angular speed

 ω =  α  x t

 ω = 0.19 x 2.46

 ω = 0.467 rad/s

7 0
3 years ago
What would be an example of a chemical change that took a long time to occur
weqwewe [10]
<span>rusting takes a long time, and rusting is a chemical change</span>
3 0
3 years ago
Read 2 more answers
Choose the statement(s) that is/are true about the ratio \frac{C_p}{C_v} C p C v for a gas? (Ii) This ratio is the same for all
Blababa [14]

Answer:

(i) false

(ii) true

(iii) true

(iv) false

Explanation:

(i) The ratio of Cp and Cv is not constant for all the gases. It is because the value of cp and Cv is different for monoatomic, diatomic and polyatomic gases.

So, this is false.

(ii) For monoatomic gas

Cp = 5R/2, Cv = 3R/2

So, thier ratio

Cp / Cv = 5 / 3 = 1.67

This statement is true.

(iii) for diatomic gases

Cp = 7R/2, Cv = 5R/2

Cp / Cv = 7 / 5 = 1.4

This statement is true.

(iv) It is false.

6 0
3 years ago
What does it mean to say the mass is conserved during a physical change ?
Olin [163]
Mater doesn't just appear or disappeared. Chemical elements are still there just the connections and how it combines changes.

So what goes into your chemical eqation must still exist after the change.
4 0
3 years ago
Read 2 more answers
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