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trasher [3.6K]
2 years ago
6

(b) How much energy must be supplied to boil 2kg of water? providing that the specific latent heat of vaporization of water is 3

30 kJ/kg.
Physics
1 answer:
Lelu [443]2 years ago
8 0

Complete question:

(b) How much energy must be supplied to boil 2kg of water? providing that the specific latent heat of vaporization of water is 330 kJ/kg. The initial temperature of the water is 20 ⁰C

Answer:

The energy that must be supplied to boil the given mass of the water is 672,000 J

Explanation:

Given;

mass of water, m = 2 kg

heat of vaporization of water, L =  330 kJ/kg

initial temperature of water, t = 20 ⁰C

specific heat capacity of water, c = 4200 J/kg⁰C

Assuming no mass of the water is lost through vaporization, the energy needed to boil the given water is calculated as;

Q = mc(100 - 20)

Q = 2 x 4200 x (80)  

Q = 672,000 J

Q = 672,000 J

Q = 672,000 J

Therefore, the energy that must be supplied to boil the given mass of the water is 672,000 J

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Assume that the physics instructor would like to have normal visual acuity from 21 cm out to infinity and that his bifocals rest
shutvik [7]

This is note the complete question, the complete question is:

One of the lousy things about getting old (prepare yourself!) is that you can be both near-sighted and farsighted at once. Some original defect in the lens of your eye may cause you to only be able to focus on some objects a limited distance away (near-sighted). At the same time, as you age, the lens of your eye becomes more rigid and less able to change its shape. This will stop you from being able to focus on objects that are too close to your eye (far-sighted). Correcting both of these problems at once can be done by using bi-focals, or by placing two lenses in the same set of frames. An old physicist instructor can only focus on objects that lie at distance between 0.47 meters and 5.4 meters.

Assume that the physics instructor would like to have normal visual acuity from 21 cm out to infinity and that his bifocals rest 2.0 cm from his eye. What is the refractive power of the portion of the lense that will correct the instructors nearsightedness?

Answer:  3.04 D

Explanation:

when an object is held 21 cm away from the instructor's eyes, the spectacle lens must produce 0.47m ( the near point) away.

An image of 0.47m from the eye will be ( 47 - 2 )

i.e 45 cm from the spectacle lens since the spectacle lens is 2cm away from the eye.

Also, the image distance will become negative

gap between lense and eye = 2cm

Therefore;

image distance d₁ = - 45cm = - 0.45m

object distance  d₀ = 21 - 2 = 19cm = 0.19m

P = 1/f = 1/ d = 1/d₀ + 1/d₁ = 1/0.19 + (-1/0.45)

P = 1/f =  5.26315789 - 2.22222222

P = 1/f = 3.04093567 ≈ 3.04 D

5 0
3 years ago
Starting from the front door of your ranch house, you walk 50.0 m due east to your windmill, and then you turn around and slowly
Hunter-Best [27]

Answer:

Average velocity

v=\frac{d}{t}\\ v=\frac{10m}{70s}\\v=.1428 \frac{m}{s}

Average speed,

S=\frac{D}{t}\\ S=\frac{90}{70}\\ S=1.29\frac{m}{s}

Explanation:

(a)Average velocity

We have to find the average velocity. We know that velocity is defined as the rate of change of displacement with respect to time.

To find the average velocity we have to find the total displacement.

since displacement along east direction is 50m

and displacement along west=40m

so total displacement,

d=50m-40m\\d=10m

total time,

t=28 s+42 s\\t=70 s

therefore, average velocity

v=\frac{d}{t}\\ v=\frac{10m}{70s}\\v=.1428 \frac{m}{s}

(b)Average Speed:

Average speed is defined as the ratio of total distance to the total time

it means

Average speed= total distance/total time

here total distance,

D= 50m+40m\\D=90m

and total time,

t= 28s+40s\\t=70s

therefore,

Average speed,

S=\frac{D}{t}\\ S=\frac{90}{70}\\ S=1.29\frac{m}{s}

8 0
3 years ago
The internal pressure on a bottle of soda is 5550 torr. the bottle cap is designed to withstand a pressure of 7.2 atm. (a) calcu
Mademuasel [1]

This is a conversion problem. 760 Torr is equal to 1 atmosphere. so we can can solve now. 5,550torr*(1atmosphere/760torr)=7.3atmospheres. since the two torrs cancel out with cross multiplication we are left in atmosphere units.

6 0
2 years ago
Read 2 more answers
A neutron star has more mass then what and is about the same size as what?
Alex_Xolod [135]
A neutron star has more mass than a bowling ball,
and is about the same size as Chicago.
5 0
3 years ago
You are given two converging lenses to build a compound microscope. Lens A has focal length 0.50 cm and lens B has focal length
siniylev [52]

Answer:

The lens to be used for the objective is lens A

Explanation:

The objective of a compound microscope

The focal length of the lens used for the objective = 1/(magnification obtained)

The focal length of most modern is equal to the tube length

The range of sizes for the focal length of a microscope is between 2 mm and 40 mm

Therefore, the appropriate lens to be used for the objective of the compound is lens A that has a focal length of 0.50 cm = 5 mm

6 0
3 years ago
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