# In which circumstances is work done?

• mehmet
In summary: A person pushing a weight up a hillWork is done when a force is applied that overcomes the natural tendency of an object to stay at its original state. In this case, the person pushing the weight is applying a force that is greater than the force of gravity, so the object moves up.c. A rock sitting on a tableIn this case, gravity is the force that is trying to keep the rock at the table. The rock has mass and gravity is trying to pull it down to the ground. But since the rock is sitting on the table, there is also a force trying to push it upwards. This is the normal force, which is the force that we experience every day when
mehmet
Homework Statement
In which of the following circumstances is work done? If work is being done, what is the force acting on the object in each case?

a. A rocket accelerating from the launch pad
b. A ski-tow hauling a skier up a ski slope
c. A skier going down the slope at a steady speed
d. A book resting on a table
e. A rocket traveling through space at a steady velocity remote from any planet or stars.
Relevant Equations
Work done = F x d (force x distance)
So I have honestly no idea what kind of force is acting on the objects in each case, nor if work is being done. I attempted to identify the force for ‘d’ and I wrote the following: “work is being done and forces acting on the book are balanced, the weight of the book acts downwards and the normal reaction acts upwards which causes the book to rest on the table, this is gravitational force as it pulls the mass together and doesn’t push them apart. However, this makes no sense to me.

mehmet said:
forces acting on the book are balanced, the weight of the book acts downwards and the normal reaction acts upwards which causes the book to rest on the table,
For "d", this part is correct. There are two forces acting on the book: Its weight (gravity) acting down and the normal force acting up. And they balance, so there's no net force.

But is work being done? For work to be done, there must be a displacement.

mehmet said:
So I have honestly no idea what kind of force is acting on the objects in each case,

For a) ..

There are two forces that must be overcome. One is present even when the rocket is stationary on the pad. The other force is because the rocket has mass and the problem says it's accelerating. What force does the rocket generate to overcome these two?

mehmet said:
Problem Statement: In which of the following circumstances is work done?

a. A rocket accelerating from the launch pad
It happens not to matter for answering the question, but the wording is rather loose. It should be clearer about whether we are discussing work done by the rocket engine or work done on the rocket mass (as opposed to its exhaust). If the engine were only firing strongly enough to keep the rocket moving at constant velocity, the engine would still be doing a great deal of work, but none on the rocket.

## 1. What is work and how is it defined in the scientific context?

In the scientific context, work is defined as the transfer of energy from one object to another, resulting in the movement of the object. It is typically measured in joules (J) and is calculated by multiplying the force applied to an object by the distance the object moves in the direction of the force.

## 2. What is the relationship between work and energy?

Work and energy are closely related concepts. Energy is the ability to do work, and work is the transfer of energy. In order for work to be done, energy must be transferred from one object to another. The amount of work done is equal to the change in energy of the object.

## 3. How is work calculated in different circumstances?

The calculation of work depends on the specific circumstances. In general, work is calculated by multiplying the force applied to an object by the distance the object moves in the direction of the force. However, in certain situations, such as when the force is not constant or when the direction of the force is not in the same direction as the movement, other formulas may be used.

## 4. Can work be negative?

Yes, work can be negative. This occurs when the force applied to an object is in the opposite direction of the movement. In this case, the work is considered to be negative because the energy is transferred away from the object instead of towards it.

## 5. In what circumstances is work not done?

Work is not done when there is no movement or displacement of an object. For example, if someone pushes against a wall but the wall does not move, no work is done because there is no displacement. Similarly, if an object is held in place by an equal and opposite force, no work is done as the object does not move.

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