What is Work & Heat? Homework Explained

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In summary, according to the physics textbook, work is the energy transferd to or from an object by means of a force acting on the object. Heat is the transfer of energy from a hot object to a cold object. Work is also done as a result of motion against an opposing force. Energy is transferred to the motion of atoms and molecules.
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DiamondV
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Homework Statement


After looking through several websites, everyone seems to have their own interpertation of this. My physics textbook says that Work is the change in energy, some people online say that Work is a form of energy and Heat can be changed into work and vice versa. My chemistry book says that Heat is the transfer of energy from a hot object to cold object as a result of the temp. difference between them. It also ssays Work is done as a result of motion against an opposing force. Some others online say that Energy is transferred to the motion of atoms and molecules. Others say that Work is energy transferred to motion of objects. HELP

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  • #2
I would like to sort of settle on two definitions. I found this one in another physics place. Work is the energy transferd to or from an object by means of a force acting on the object. Is this correct?
 
  • #3
DiamondV said:
I would like to sort of settle on two definitions. I found this one in another physics place. Work is the energy transferd to or from an object by means of a force acting on the object. Is this correct?
When you had freshman physics, what was the definition of work?
 
  • #4
Chestermiller said:
When you had freshman physics, what was the definition of work?

Every year with different teachers etc. everyone changes their definitions. I think I learned this first, Work is the ability to transfer energy or something like that.
 
  • #5
DiamondV said:
Every year with different teachers etc. everyone changes their definitions. I checked again, this is the one I probably learned first Work is the energy transferred to or from an object by means of a force acting on it.
And this is the definition of work they taught you in freshman physics?
 
  • #6
Chestermiller said:
And this is the definition of work they taught you in freshman physics?
Don't exactly know what freshman physics is. I am assuming that's American education system. I am in Europe.
 
  • #7
That was probably the earliest definition I could recall.
 
  • #8
DiamondV said:
Don't exactly know what freshman physics is. I am assuming that's American education system. I am in Europe.
So you never heard of work equals force times distance?
 
  • #9
Chestermiller said:
So you never heard of work equals force times distance?
Yes I have. W=Fd. They usually tell us both equation and worded definitions
 
  • #10
DiamondV said:
Yes I have. W=Fd. They usually tell us both equation and worded definitions
OK. So we are on the same page. The work is a macroscopic quantity. In thermodynamics, it is also force times distance. In the case of thermodynamics, we often get the work as W = PΔV, where p is the pressure (force per unit area) and ΔV is the change in volume. Note that pressure is force divided by area, while change in volume is displacement time area. So, it's really the same thing.

Now for heat. Do you remember from freshman physics when you had one end of a rod at a high temperature and the other end of the rod at a low temperature? We said that the rate of heat flow was equal to the cross sectional area times the thermal conductivity k times the temperature difference divided by the length of the rod. We called this the rate of heat conduction. This is the same kind of thing that happens thermodynamics when we talk about heat flow.

Chet
 

FAQ: What is Work & Heat? Homework Explained

What is the difference between work and heat?

Work and heat are both forms of energy, but they differ in how they are transferred. Work is the transfer of energy that occurs when a force is applied to an object and it moves in the direction of the force. Heat, on the other hand, is the transfer of energy that occurs between two objects at different temperatures. It is transferred from the warmer object to the cooler object until they reach thermal equilibrium.

How is work and heat related to thermodynamics?

Thermodynamics is the study of the relationship between heat, work, and other forms of energy. The first law of thermodynamics states that energy cannot be created or destroyed, but can only be transferred or converted from one form to another. Work and heat are two ways that energy can be transferred, and they play a crucial role in many thermodynamic processes.

Can you give an example of work and heat in everyday life?

One example of work in everyday life is when you push a shopping cart through a store. The force you apply to the cart causes it to move, and this transfer of energy is considered work. An example of heat transfer is when you put a hot pot on a stove. The heat from the stove is transferred to the pot, causing it to heat up and eventually cook your food.

How do work and heat affect the temperature of a system?

Work and heat can both cause changes in the temperature of a system. When work is done on a system, such as compressing a gas, its temperature increases. This is because the energy from the work is converted into thermal energy. Similarly, when heat is added to a system, its temperature increases as the molecules within the system gain more kinetic energy.

What are the units of measurement for work and heat?

The SI unit for work is the joule (J), which is defined as the amount of work done when a force of one newton is applied over a distance of one meter. The unit for heat is the calorie (cal) or its multiples, such as the kilocalorie (kcal). One calorie is defined as the amount of heat needed to raise the temperature of one gram of water by one degree Celsius.

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