# Quick questions on work and energy

• future_vet
In summary, work cannot be done on a system without motion, but there are other ways to increase the energy of a system. A system can have negative potential energy due to the arbitrary choice of zero potential energy. In the case of the elevator, the work done by the 550N force is approximately 3.00x 104 J.

#### future_vet

Can work be done on a system if there is no motion?
I would say no, no motion = no energy...

Is it possible for a system to have negative potential energy?
I would say yes, since the choice of the zero of potential energy is arbitrary.

A 500-kg elevator is pulled upward with a constant force of 550N for a distance of 50 m. What is the work done by the 550N force?
From what I understand, we multiply 550N by 50 m, and get about 3.00x 104 J.

I think you are pretty much correct.

I would agree with you on all three. But the first question is thought provoking. I wonder if we can think of a case where there is work done, but no motion. Certainly that is true in cases where there is no *net* motion, like spinning a wheel with friction bearings. But no motion at all...hmmm.

Chemical energy conversion...is that considered work? I don't think so, but maybe someone else can think of a creative case.

Thank you!

future_vet said:
Can work be done on a system if there is no motion?
I would say no, no motion = no energy...

You can't do mechanical work without motion, but there are other ways to increase the energy of a system - for example adding heat energy, or storing electrical charge in a capacitor. "Increasing the energy" is the same as "doing work".

Is it possible for a system to have negative potential energy?
I would say yes, since the choice of the zero of potential energy is arbitrary.

A 500-kg elevator is pulled upward with a constant force of 550N for a distance of 50 m. What is the work done by the 550N force?
From what I understand, we multiply 550N by 50 m, and get about 3.00x 104 J.

Both correct.

## 1. What is work?

Work is defined as the application of a force over a distance. In simpler terms, work is the energy required to move an object.

## 2. How is work calculated?

Work is calculated by multiplying the force applied to an object by the distance the object is moved in the direction of the force. The formula for work is W = F * d.

## 3. What is energy?

Energy is defined as the ability to do work. It is a fundamental concept in physics and is measured in joules (J).

## 4. How is energy related to work?

Energy and work are closely related. Work is the transfer of energy from one object to another, or the conversion of energy from one form to another. In other words, work uses energy to make something happen.

## 5. What are the different types of energy?

There are several types of energy, including kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat energy), chemical energy (energy stored in bonds between atoms), and electrical energy (energy carried by moving electrons).