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nlexa [21]
3 years ago
9

A string is being pulled with a force of 20 N and moves a 5 kg block to the left at a constant speed. What is the coefficient of

friction for between the floor and the block? Enter your answer as a decimal value (Example: 0.72) * I think the answer is 20 but this question is starting frustrating me
Physics
1 answer:
Valentin [98]3 years ago
6 0

Answer:

μ = 0.4

Explanation:

As, the object is moving at a constant speed. Therefore, the unbalanced force on it must be equal to zero. So, the frictional force on the object must be equal to the force applied to it:

F = frictional force

F = μR = μW = μmg

where,

F = Applied Force  = 20 N

μ = coefficient of friction between wall and floor = ?

m = mass of block = 5 kg

g = 9.8 m/s²

Therefore,

20 N = μ(5 kg)(9.8 m/s²)

μ = 20 N/49 N

<u>μ = 0.4</u>

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A highly volatile substance has an initial mass of 1200 g and its mass is reduced by 12% each second.
Softa [21]

Answer:

Explanation:

a) 1.00 - 0.12 = 0.88

m = 1200(0.88)^t

b) t = ln(m/1200) / ln(0.88)

c) m = 1200(0.88)^10 = 334.20 g

d) t = ln(10/1200) / ln(0.88) = 37.451... = 37 s

e) t = ln(1/1200) / ln(0.88) = 55.463... = 55 s

4 0
3 years ago
] A new coal-fired 750 MWe power plant with a thermal efficiency of 42% burns 9000 Btu/lb coal, which contains 1.1% sulfur. a. I
Valentin [98]

Answer:

The net emissions rate of sulfur is 1861 lb/hr

Explanation:

Given that:

The power or the power plant = 750 MWe

Since the power plant with a thermal efficiency of 42% (i.e. 0.42) burns 9000 Btu/lb coal, Then the energy released per one lb of the coal can be computed as:

\mathtt{=( 0.42\times 9000\times 1055.06) J}

= 3988126.8  J

= 3.99 MJ

Also, The mass of the burned coal per sec can be calculated by dividing the molecular weight of the power plant by the energy released per one lb.

i.e.

The mass of the coal that is burned per sec =\dfrac{750}{3.99}

The mass of the coal that is burned per sec = 187.97 lb/s

The mass of sulfur burned  = \dfrac{1.1}{100} \times 187.97 \  lb/s

= 2.067 lb/s

To hour; we have:

= 7444 lb/hr

However, If a scrubber with 75% removal efficiency is utilized,

Then; the net emissions rate of sulfur is (1 - 0.75) × 7444 lb/hr

= 0.25 × 7444 lb/hr

= 1861 lb/hr

Hence, the net emissions rate of sulfur is 1861 lb/hr

8 0
3 years ago
Se dispone de dos vasos con agua a 20 grados y queremos calentarlo hasta alcanzar 50 grados. Si el primero contiene 0,5l y el se
BigorU [14]

Answer:

The cup with 0.5L

Explanation:

To know what amount of water you take into account the specific heat of the water. The specific heat of water is:

c_{water}=4186\frac{J}{kg\°C}

Thus, 4186 J of energy are needed to icrease the temperature of 1 kg water in 1°C. Then, more grams of water will need more energy.

You have that one cup has 0.5 L and the other one has 750mL = 0.75L

The second cup of water will need more heat because the amount of water contained in the second cup is greater than in the first cup with 0.5L

4 0
3 years ago
If state law mandates that elevators cannot accelerate more than 4.80 m/s2 or travel faster than 19.8 m/s , what is the minimum
Rudik [331]

Answer:

23.0 s

Explanation:

Given:

v₀ = 0 m/s

v = 19.8 m/s

a = 4.80 m/s²

Find: Δx and t

v² = v₀² + 2aΔx

(19.8 m/s)² = (0 m/s)² + 2 (4.80 m/s²) Δx

Δx = 40.84 m

v = at + v₀

19.8 m/s = (4.80 m/s²) t + 0 m/s

t = 4.125 s

The elevator takes 40.84 m and 4.125 s to accelerate, and therefore also 40.84 m and 4.125 s to decelerate.

That leaves 291.3 m to travel at top speed.  The time it takes is:

291.3 m / (19.8 m/s) = 14.71 s

The total time is 4.125 s + 14.71 s + 4.125 s = 23.0 s.

8 0
3 years ago
Can somebody answer this for me asap!
andreev551 [17]
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7 0
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