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3 years ago

An elevator weighs 1500 Newtons. Calculate how much potential energy it has when it is lived 500 meters in the air.

Physics

1 answer:

avanturin [10]3 years ago

4 0

An elevator has 750,000 J when it is lived 500 meters in the air

Answer: Option D

<u>Explanation:</u>

The expression to find the potential energy completely on the basis of forces that on two objects. It can be written as

$potential\ energy (P . E)=m \times acceleration\ due\ to\ gravity\ (g) \times height (h)$

Where,

m – mass of object

Acceleration due to gravity = $9.8 \mathrm{m} / \mathrm{s}^{2}$

h = 500 meters

Force = 1500 Newton

As we know, according to Newton second law of motion, the force can be expressed in terms of mass and gravity (F= ma). So, the potential energy can be calculated as

$P . E=F \times h=1500(500)=750000 J$

Hence, an elevator has 750,000 J when it is lived 500 meters in the air.

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3 years ago

A frictionless piston-cylinder device contains 10 kg of superheated vapor at 550 kPa and 340oC. Steam is then cooled at constant

Alla [95]

Answer:

a) the work (W) done during the process is -2043.25 kJ

b) the work (W) done during the process is -2418.96 kJ

Explanation:

Given the data in the question;

mass of water vapor m = 10 kg

initial pressure P₁ = 550 kPa

Initial temperature T₁ = 340 °C

steam cooled at constant pressure until 60 percent of it, by mass, condenses; x = 100% - 60% = 40% = 0.4

from superheated steam table

specific volume v₁ = 0.5092 m³/kg

so the properties of steam at p₂ = 550 kPa, and dryness fraction

x = 0.4

specific volume v₂ = v $_f$ + xv $_{fg$

v₂ = 0.001097 + 0.4( 0.34261 - 0.001097 )

v₂ = 0.1377 m³/kg

Now, work done during the process;

W = mP₁( v₂ - v₁ )

W = 10 × 550( 0.1377 - 0.5092 )

W = 5500 × -0.3715

W = -2043.25 kJ

Therefore, the work (W) done during the process is -2043.25 kJ

( The negative, indicates work is done on the system )

What would the work done be if steam were cooled at constant pressure until 80 percent of it, by mass, condenses

x₂ = 100% - 80% = 20% = 0.2

specific volume v₂ = v $_f$ + x₂v $_{fg$

v₂ = 0.001097 + 0.2( 0.34261 - 0.001097 )

v₂ = 0.06939 m³/kg

Now, work done during the process will be;

W = mP₁( v₂ - v₁ )

W = 10 × 550( 0.06939 - 0.5092 )

W = 5500 × -0.43981

W = -2418.96 kJ

Therefore, the work (W) done during the process is -2418.96 kJ

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3 years ago

Many species cool themselves by sweating, because as the sweat evaporates, heat is transferred to the surroundings. A human exer

max2010maxim [7]

Answer:

70713

Explanation:

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3 years ago

Potassium-40 has a half-life of approximately 1.25 billion years. Approximately how many years will pass before a sample of pota

Maksim231197 [3]

Answer:

3.75 billion years

Explanation:

From the question given above, the following data were obtained:

Half-life (t½) = 1.25 billion years

Number of half-lives (n) = 3

Time (t) =?

The time taken for the sample of potassium-40 to contains one-eighth the original amount of parent isotope can be obtained as:

n = t / t½

3 = t / 1.25

Cross multiply

t = 3 × 1.25

t = 3.75 billion years.

Therefore, it will take 3.75 billion years for the sample of potassium-40 to contains one-eighth the original amount of parent isotope

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3 years ago