A gasoline engine operates at a temperature of 270°C and exhausts at 210°C. Calculate the maximum efficiency of this engine. (Note that the Celsius scale is used.)89.0 %
88.0 %
12.0 %
11.0 %
Answers
Answer:
Hello! the efficiency of a thermal engine depends on how much of the initial input is transformed into work, Here 270°c is the input and 210°c is the output.
Then the efficiency is calculated as e = 1 - Tc/Th, where Th is the hot temperature (in this case 270°C) and Tc is the cold temperature (in this case 210°C)
First we need to write the temperatures in kelvin degrees, this can be done by adding 273.15 to the celsius scale:
Th = 270 + 273.15 = 543.15
Tc = 210 +273.15 = 483.15
then the efficiency is e = 1 - 543.15/483.15 = 0.11
if we write this as a percentage, we get an efficiency of 11%, then the fourth answer is the correct one.
Answer:
Given:
Th = 270 °C = 270+273 = 543 K, hot temperature
Tc = 210 °C = 210+273 = 363 K, cold temperature
According to the Carnot theorem, the maximum efficiency achievable by a heat engine between a hot and cold temperature is
η = 1 - Tc/Th
= 1 - 363/543
= 0.668 = 11.047 (approx)
Answer: 11.0% (nearest integer)
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What is a physical form in which a substance can exist?
A) Joe is right because the electricity is changed to heat and light and is no longer electricity.
B)Ben is right because the Law of Conservation of Energy is a law and cannot be false.
C) Ben is right because the electricity from the light is transformed into heat and light.
D) Joe is right because all electrical lights and appliances use electricity.
2) Greg and Shawn are studying for a physical science test. Greg thinks that the kinetic energy of an object depends on the height and speed of an object, but Shawn thinks it depends on the mass of an object. Who is right and why?
A) Shawn is right. The mass of an object determines the inertia of the object. Increasing inertia is the only thing that will increase kinetic energy..
B) Both Greg and Shawn are correct since kinetic energy depends on mass, height and speed of an object.
C) Greg is right. Increasing the height or speed of an object increases the kinetic energy of an object.
D) Neither is completely right. Shawn is partly correct since kinetic energy depends on mass, but Greg is also partly right since it also depends on speed.
3) Dan got into his car in the middle of summer. When he sat on the hot black leather seats, he burned his legs. His sister said that conduction was the reason Dan burned his legs, but Dan blamed the sunshine and said it was radiation that caused him to get burned. Who was right and why?
A) Both Dan and his sister are right. The sun heated the car seats through radiation heat transfer, but then Dan touched the seat and the heat was conducted to his legs.
B) Dan's sister was correct because Dan's legs touched the car seats. That is an indicator of heat transfer by conduction.
C) Dan was right because the sun heated the car without touching it. That is radiation.
D) Dan's sister was right because conduction can transfer heat through both solids and fluids (such as air).
Answers
1) C) Ben is right because the electricity from the light is transformed into heat and light.
Explanation:
The Law of Conservation of Energy states that energy cannot be created nor destroyed, but only transformed.
In this particular example, energy is not destroyed. In fact, the electrical energy (produced, for instance, by the battery inside the torchlight) is converted into light (electromagnetic wave) and heat (thermal energy). So, Ben is right, because energy is just transformed into other types of energy.
2) D) Neither is completely right. Shawn is partly correct since kinetic energy depends on mass, but Greg is also partly right since it also depends on speed.
Explanation:
The kinetic energy of an object is given by:
where m is the mass of the object and v its speed. From the formula, we see that neither Shawn nor Greg is completely right, because the kinetic energy depends both on the mass and the speed, and:
- Greg only told about the speed
- Shawn only told about the mass
3) B) Dan's sister was correct because Dan's legs touched the car seats. That is an indicator of heat transfer by conduction.
Explanation:
Conduction is the method of heat transfer that occurs between two solid objects, when they are in contact with each other, and it is due to the collisions between the molecules of the two objects: when colliding, the molecules of the hotter object transfer part of their kinetic energy to the molecules of the colder object.
In this case, Dan legs are in contact with the car seat (which is at higher temperature), so heat is transferred from the seat to Dan legs by conduction.
3 is B my dude and the reason nobody answered is because thousands of questions are asked every day. So not every question can be answered. It doesn't have to do with being lazy.
Answers
Answers
Frequency of a wave =
(speed of the wave) divided by (wavelength)
or
(1) divided by (period of the wave) .
Period of the wave =
(wavelength) divided by (speed of the wave)
or
(1) divided by (frequency of the wave) .
Answers
Considering the definition of density, the density of the old coin is 8.92 .
It is neccesary to know that density is defined as the property that matter, whether solid, liquid or gas, has to compress into a given space.
In other words, Density is a quantity that allows us to measure the amount of mass in a certain volume of a substance, that is, density is the relationship between the mass of a substance and the volume it occupies.
Mathematically, the expression for the calculation of density is the quotient between the mass of a body and the volume it occupies:
In this case, you know:
- mass= 26.76 g
- volume= 3 cm³
Replacing in the definition of density:
Solving:
density= 8.92
The density of the old coin is 8.92 .
Learn more about density:
Density = mass/volume
26.76/3 = 8.92
The density is 8.92
Answers
441 N = m* 9.8
9.8m = 441
m = 441/9.8
m = 45 kg.
Mass of the dog is = 45 kg