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ArbitrLikvidat [17]
3 years ago
15

Why is random sampling and random assignment in experimental research important?

Physics
1 answer:
Hunter-Best [27]3 years ago
6 0

So the result is not biased or affected in some way

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Tĩnh lực tĩnh điện [lực cu lông] giữa 2 điện tích điểm q1,q2 biết q1=2.10-9 q2=4.10-9 r=3cm
Anettt [7]
  • q1=2×10^{-9}C
  • q2=4×10^{-9}C
  • Radius=3cm=0.3m

Using coulmb's law

\\ \bull\tt\dashrightarrow F=k\dfrac{q1q2}{r^2}

\\ \bull\tt\dashrightarrow F=8.98\dfrac{2\times 10^{-9}\times 4\times 10^{-9}}{(0.3)^2}

\\ \bull\tt\dashrightarrow F=8.98\dfrac{8\times 10^{-18}C^2}{0.09m^2}

\\ \bull\tt\dashrightarrow F=\dfrac{71.84\times 10^{-18}C^2}{0.09m^2}

\\ \bull\tt\dashrightarrow F=798.2\times 10^{18}Nm^2/C^2

\\ \bull\tt\dashrightarrow F=7.9\times 10^{16}Nm^2/C^2

6 0
3 years ago
A pupil adds 37g of ice at 0°C to 100g of water at 30°C. The final temperature of the water and melted ice is 0°C. no heat is lo
mojhsa [17]

Answer:

The specific latent heat of ice is approximately 341 J/g

The correct option is;

b) 341 J/g

Explanation:

The given parameters are;

The mass of ice the pupil adds to the water, m₁ = 37 g

The initial temperature of the ice, T₁ = 0°C

The mass of the water to which the ice is added, m₂ = 100 g

The initial temperature of the water, T₂₁ = 30°C

The final temperature of the water and the melted ice, T₂₂ = 0°C

The specific heat capacity of the water, c₂ = 4.2 J/(g·°C)

By the principle of conservation of energy, we have;

The heat gained by the ice = The heat lost by the water = ΔQ₂

Given that the ice is only melted with no change in temperature, we have;

The heat gained by the ice = The latent heat needed for melting the ice

ΔQ₂ = m₂ × c₂ × (T₂₂ - T₂₁) = 100 × 4.2 × (0 - 30) = -12,600 J

The heat gained by the ice = m₁ × L_f

Where;

L_f represents the specific latent heat of fusion of ice;

We have;

12,600 = 37 × L_f

L_f = 12,600/37 = 340.54 J/g ≈ 341 J/g

The specific latent heat of fusion of ice = L_f ≈ 341 J/g.

5 0
3 years ago
Am I the only one or do I hate scooping the cat box if you guys have cats.​
LenaWriter [7]
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4 0
3 years ago
Read 2 more answers
A downhill skier was able to move 560 meters in 25 seconds. What is the skier’s average speed? (Round your answer to the nearest
slava [35]
Speed is distance in a specific time period. When someone ask use the unit "m/s" this period of time is one second. If the skier was able to move 560 m in 25 seconds, in one second how much distance he moves? That is the question.
You can solve this problem like
560m/25s = 22,4 m/s
Good luck!

6 0
3 years ago
Read 2 more answers
A woman 5.5 ft walks at a rate of 6 ft/sec towards a street light that is 22 ft above the ground. At what rate is the length of
Soloha48 [4]

Answer:

The length of her shadow is changing at the rate  -2 m/s

Explanation:

Let the height oh the street light, h = 22 ft

Let the height of the woman, w = 5.5 ft

Horizontal distance to the street light = l

length of shadow = x

h/w = (l + x)/x

22/5.5 =  (l + x)/x

4x = l + x

3x = l

x = 1/3 l

taking the derivative with respect to t of both sides

dx/dt = 1/3 dl/dt

dl/dt = -6 ft/sec ( since the woman is walking towards the street light, the value of l is decreasing with time)

dx/dt = 1/3 * (-6)

dx/dt = -2 m/s

7 0
3 years ago
Read 2 more answers
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