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4 years ago

What can keep ice from melting

Physics

1 answer:

Tcecarenko [31]4 years ago

5 0

Since my answer can’t be two words it’s a freezer or a fridge or just a cold place

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How many electrons does a neutral atom of sudium-25 have

horrorfan [7]

Answer:

Option A. 11

Explanation:

The atomic number of an element does not change.

Recall:

Atomic number = proton number

If the atom is neutral, then,

Proton number = electron number

Since the element is sodium, then, the atomic number of sodium–25 is 11.

Also, we were told to obtain the electrons of a neutral atom of sodium–25

Therefore,

Atomic number = proton number = 11

Since the atom is neutral,

Proton number = electron number = 11

8 0

3 years ago

One bright summer day a swimmer is floating with her head just above the surface of a large, clear lake where the water has inde

slavikrds [6]

Answer:

5.38035 m

Explanation:

$n_w$ = Refactive index of water = 1.43

h = Depth = 5.5 m

Critical angle is given by

$\theta_c=sin^{-1}\dfrac{1}{n_w}\\\Rightarrow \theta_c=sin^{-1}\dfrac{1}{1.43}\\\Rightarrow \theta_c=44.37^{\circ}$

d = horizontal distance from the post where she no longer see the bottom of wooden post

So,

$tan\theta_c=\dfrac{d}{h}\\\Rightarrow d=tan\theta_c\times h\\\Rightarrow d=tan44.37\times 5.5\\\Rightarrow d=5.38035\ m$

The distance d is 5.38035 m

4 0

3 years ago

What relationship exists betwen air resistance and acceleration of falling objects

ololo11 [35]

They both make a thing go faster and slower but the relationship is force.

5 0

4 years ago

Read 2 more answers

A fisherman notices that his boat is moving up and down periodically without any horizontal motion, owing to waves on the surfac

azamat

Answer:

a. Speed = 1.6 m/s

b. Amplitude = 0.3 m

c. Speed = 1.6 m/s

Amplitude = 0.15 m

Explanation:

The frequency of the wave must be equal to the reciprocal of the time taken by the boat to move from the highest point to the highest point again. This time will be twice the value of the time taken to travel from the highest point to the lowest point:

frequency = $\frac{1}{2(2\ s)}$ = 0.25 Hz

The wavelength of the wave is the distance between consecutive crests of wave. Therefore,

Wavelength = 6.4 m

Now, the speed of the wave is given as:

Speed = (Frequency)(Wavelength)

Speed = (0.25 Hz)(6.4 m)

Speed = 1.6 m/s

Amplitude is the distance between the mean position of the wave and the extreme position. Hence, it will be half the distance between the highest and lowest point:

Amplitude = (0.5)(0.6 m)

Amplitude = 0.3 m

frequency = $\frac{1}{2(2\ s)}$ = 0.25 Hz

Speed = (Frequency)(Wavelength)

Speed = (0.25 Hz)(6.4 m)

Speed = 1.6 m/s

Amplitude = (0.5)(0.3 m)

Amplitude = 0.15 m

8 0

3 years ago

A girl standing upright exerts a pressure of 15000 N/m2 on the floor. Given that the total area of contact of shoes and the floo

lapo4ka [179]

Explanation:

F=15000/0.02

=300N

total area contact of the shoes and floor when stood in one foot=0.02m^2/2=0.01m^2

P=F/A

=300/0.01

=30 000Pa/30 000Nm^-2

in another way=15000×2

=30000N/m^2

5 0

4 years ago