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3 years ago

Which one of the following energy conversion devices has the lowest energy efficiency?

Physics

1 answer:

Anna35 [415]3 years ago

3 0

Answer:

A) incandescent ligth bulb, its efficiency is about 10%

Explanation:

The incandescent bulb, that is, the well-known focus with its warm light, was one of the most useful inventions of the 19th century although its use is currently considered very inefficient. These lamps waste between 80 and 90 percent of the total electricity they consume by turning it into heat. The metal filament thus heated and which is the central part of the bulb, only converts the remaining energy into light. Its service life ranges from 750 to 1,000 hours.

This is why they are used in ovens for food preparation, because of the large amount of heat they generate.

The steam boiler in a power plant depends on the fuel that it is using, but a coal-fired power plant with modern technology its efficiency is about 40%

Electric motor are around 85-92%

In order to better understand the concept of efficiency it is as if we pay 100 dollars of gasoline for our weekly use, but of that 100 dollars the car only uses 10 dollars to do that activity the rest of the money the 90 dollars were lost because of the inefficiencies of the vehicle.

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An iron nail is driven into a block of ice by a single blow of a hammer. The hammerhead has a mass of 0.5 kg and an initial spee

larisa [96]

Answer:

The ice melts mass is:

$m_g=7.6x10^{-3} g$

Explanation:

Kinetic Energy

$K_E = 1/2*m*v^2$

$K_E = 1/2*0.5kg*(3.2m/s)^2$

$K_E=2.56 kg*m^2/s^2$

Heat gained by ice= mass(g) x 80 cal

( 1 cal = 4.184 *10^7er or g cm^2/ sec^2)

Assuming no loss in heat, in the motion so both continue with temperature 0~C

To find so the mass (gm) of ice melted

$m_g= 1/2 *(0.5*1000)*(3.2m/s)^2* 100*100 / (80*4.184*10^7)$

$m_g=7.6x10^{-3} g$

5 0

3 years ago

An automobile of mass 2000 kg moving at 30 m/s is braked suddenly with a constant braking force of 10000 N. How far does the car

saveliy_v [14]

Answer:

The car traveled the distance before stopping is 90 m.

Explanation:

Given that,

Mass of automobile = 2000 kg

speed = 30 m/s

Braking force = 10000 N

For, The acceleration is

Using newton's formula

$F = ma$

Where, f = force

m= mass

a = acceleration

Put the value of F and m into the formula

$-10000 =2000\times a$

Negative sing shows the braking force.

It shows the direction of force is opposite of the motion.

$a = -\dfrac{10000}{2000}$

$a=-5\ m/s^2$

For the distance,

Using third equation of motion

$v^2-u^2=2as$

Where, v= final velocity

u = initial velocity

a = acceleration

s = stopping distance of car

Put the value in the equation

$0-30^2=2\times(-5)\times s$

$s = 90\ m$

Hence, The car traveled the distance before stopping is 90 m.

6 0

3 years ago

Which statement best describes perigee? A) The closest point in Earth's orbit of the Sun. B) The farthest point in the Moon's or

iragen [17]

The correct answer is D) The closet point in the Moon's orbit to Earth

This does not refer to the Moon only. It refers to any satellite and to its closest point to Earth.

3 0

3 years ago

A microcomputer that is smaller, lighter, and less powerful than a notebook, and that has a touch sensitive screen, is called a

yKpoI14uk [10]

<span>A microcomputer that is smaller, lighter, and less powerful than a notebook, and that has a touch sensitive screen, is called a tablet. Tablets are used similarly to computers in the way that information can be stored, viewed and edited on them.</span>

8 0

3 years ago

We decided to make an iced latte by adding ice to a 200 mL hot latte at 45 °C. The ice starts out at 0 C. How much ice do we nee

tankabanditka [31]

Answer:

m = 77.75 g

Explanation:

Here we know that at equilibrium the temperature of the system will be 10 degree C

so heat given by hot latte = heat absorbed by the ice

now we have

heat given by latte = $m s\Delta T$