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qwelly [4]
3 years ago
7

Why is no work done when you hold a book in place over your head?

Physics
1 answer:
spayn [35]3 years ago
8 0
The book has no movement and there is a force that is put in to the book.
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How far will a train with a speed of 20 m/s travel in: 10s
Citrus2011 [14]

Answer:

The correct answer would be 200m

Explanation:

20x10=200

the previous answer is incorect from the other user.

8 0
3 years ago
What if energy, like electricity, could not be converted to other forms like sound, heat, motion, or light?
EleoNora [17]

Answer: It wouldn't be as modern as today is we would be back to using oil and other things from back then there wouldn't be cars everything would be less machined.

5 0
3 years ago
The eyes of some reptiles are sensitive to 850 nm light. If the minimum energy to trigger the receptor at this wavelength is 3.1
mr_godi [17]

Answer:

Minimum number of photons required is 1.35 x 10⁵

Explanation:

Given:

Wavelength of the light, λ = 850 nm = 850 x 10⁻⁹ m

Energy of one photon is given by the relation :

E=\frac{hc}{\lambda}    ....(1)

Here h is Planck's constant and c is speed of light.

Let N be the minimum number of photons needed for triggering receptor.

Minimum energy required for triggering receptor, E₁ = 3.15 x 10⁻¹⁴ J

According to the problem, energy of N number of photons is equal to the energy required for triggering, that is,

E₁ = N x E

Put equation (1) in the above equation.

E_{1}=N\times\frac{hc}{\lambda}

Substitute 3.15 x 10⁻¹⁴ J for E₁, 850 x 10⁻⁹ m for λ, 6.6 x 10⁻³⁴ J s for h and 3 x 10⁸ m/s for c in the above equation.

3.15\times10^{-14} =N\times\frac{6.6\times10^{-34}\times3\times10^{8}}{850\times10^{-9}}

N = 1.35 x 10⁵

8 0
3 years ago
What type of rays would you expect to be used frequently at a hospital to make medical diagnoses?
Bess [88]
X rays because to see your bones
7 0
4 years ago
A mountaintop is a height y above the level ground. A woman measures the angle of elevation of the mountaintop to be θ when she
valentina_108 [34]
Let t = Theta and p = Phi
Tan t = y/x    Then x =y/Tant.
Tant = y/(x-d)  x-d = y/Tanp
y/Tant  - d = y/Tanp
y -d*Tanr = y*Tant/Tanp
y-y*Tant/Tanp  =  d*Tanr
y(1 - Tanr/Tanp = d*Tant

y = d*Tant/(1-Tant/Tanp)
7 0
4 years ago
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