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jonny [76]
3 years ago
11

1. what are valence electrons?

Physics
2 answers:
Aleks04 [339]3 years ago
6 0
<span>Valence electrons are electrons in the outermost shell available for bonding</span>
In-s [12.5K]3 years ago
3 0
For number one the answer would be B

I think the second one B, 24
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A horizontal spring with stiffness 0.4 N/m has a relaxed length of 11 cm (0.11 m). A mass of 21 grams (0.021 kg) is attached and
riadik2000 [5.3K]

Answer:

0.6983 m/s

Explanation:

k = spring constant of the spring = 0.4 N/m

L₀ = Initial length = 11 cm = 0.11 m

L = Final length = 27 cm = 0.27 m

x = stretch in the spring = L - L₀ = 0.27 - 0.11 = 0.16 m

m = mass of the mass attached = 0.021 kg

v = speed of the mass

Using conservation of energy

Kinetic energy of mass = Spring potential energy

(0.5) m v² = (0.5) k x²

m v² = k x²

(0.021) v² = (0.4) (0.16)²

v = 0.6983 m/s

5 0
3 years ago
A hydrogen atom in the n=7 state decays to the n=4 state. what is the wavelength of the photon that the hydrogen atom emits? use
frez [133]

A hydrogen atom in the n=7 state decays to the n=4 state. The wavelength of the photon that the hydrogen atom emits is 4592.59nm.

The Energy of photon is the energy possessed by a photon when it moves from a high energy level to a low energy level. It emits a photon of a certain wavelength. The following relation can be used to find out the relation between the energy levels and the energy possessed:

E = 13.6 × Z² (1/n₂² - 1/n₁²) eV

where, n₁ is the initial energy level i.e. n₁ =7

            n₂ is the higher energy level i.e. n₂ = 4

            E is the energy possessed

            Z is the atomic number, Z = 1 for H-atom

Subsituting in above equation,

E = 13.6 (1/16 - 1/49) eV

E = 0.27 eV

We know that,

E = hc / λ  

where, h is Planck constant

           c is speed of light

            λ is wavelength

On subsituting,

0.27 eV = 1240/ λ

⇒ λ = 4592.59 nm

Hence, the wavelength of photon emitted by Hydrogen atom is 4592.59nm.

Learn more about Energy of Photon here, brainly.com/question/2393994

#SPJ4

 

5 0
1 year ago
If a nearsighted person has a far point df that is 3.50 m from the eye, what is the focal length f1 of the contact lenses that t
Anastaziya [24]

Answer:

f1 = -3.50 m

Explanation:

For a nearsighted person an object at infinity must be made to  appear  to be at his far point which is 3.50 m away. The image of an object at infinity must be formed on the same side of the lens as the object.

∴ v = -3.5 m

Using mirror formula,

i/f1 = 1/v + 1/u

Where f1 = focal length of the contact lens, v = image distance = -3.5 m, u =         object distance = at infinity(∞) = 1/0

∴ 1/f1 = (1/-3.5) + 1/infinity

  Note that, 1/infinity = 1/(1/0) = 0/1 =0.

∴ 1/f1 = 1/(-3.5) + 0

  1/f1 = 1/(-3.5)

Solving the equation by finding the inverse of both side of the equation.

∴ f1 = -3.50 m

 Therefore a converging lens of focal length  f1 = -3.50 m

would be needed by the person to see an object at infinity clearly

8 0
3 years ago
All of the following are changeable
Ratling [72]

Answer:

Heredity

Explanation:

Can't change the DNA you inherited the same way you can change eating habits+drug use or avoid stress

5 0
2 years ago
Read 2 more answers
An archer pulls her bowstring back 0.226 m by exerting a force that increases uniformly from zero to 263 N. What is the equivale
enyata [817]

Answer: k = 1163.72 N/m²

Explanation: if the bow obeys hook's law, then force is proportional to extension.

F = ke.

F= Force = 263 N

k = force constant

e = extension = 0.226m

263 = k * 0.226

k = 263/ 0.226

k = 1163.72 N/m²

7 0
3 years ago
Read 2 more answers
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