Work done as a function of time

In summary, the conversation discusses whether the work done on a body can be described as a function of time when a force is acting upon it. The idea of using power instead of work is also mentioned, but it depends on the situation. The concept of reaction mass and its role in rockets is also brought up. The conclusion is that in order to hold an object in place against a force like gravity, a simple connection is a more efficient option than using a rocket.
  • #1
s0ft
83
0
Hey guys, can the work done on a body be described as the function of time during which a force acts upon it?
 
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  • #2
You can do this.
It might be more useful to consider power, but that depends on the setup.
 
  • #3
I mean in a situation like where you hold an object against, say, gravity for some time would there be any work done? From what we know, until there is no motion, the work done is zero. But would it be possible to look at this problem from the "time" point of view?
For example you have a mass 'm' being attracted to another mass 'M'. You want to keep 'm' from getting to 'M'. So, say you use a rocket to push 'm', against the direction of its motion. If you manage to stop it and hold it against the gravity of 'M', would any work be done? If yes, work against what?
 
  • #4
Power is force times velocity, and power is the derivative of work done. With zero velocity, power is zero and therefore work done does not change.

A rocket has to do work in your setup, but that is used to accelerate its reaction mass.
 
  • #5
Reaction mass?
 
  • #6
That stuff which gets ejected. In chemical rockets, it is the same as its fuel. In other designs (like ion drives), it can be different.
See this explanation for details.
 
  • #7
Thanks. So basically the work done to throw the reaction mass is the work done to hold the 'm' in its place?
 
  • #8
Well, it is work done by the rocket to counter some force (here: gravity) - this just shows that rockets are a bad idea if you want to hold something in a fixed distance. A simple connection gives the same result and does not have to do work.
 

1. What is work done as a function of time?

Work done as a function of time refers to the amount of energy expended or work performed over a specific period of time. It is often measured in units such as joules per second (J/s) or watts (W).

2. How is work done as a function of time calculated?

The calculation for work done as a function of time is W = F x d, where W is work, F is force, and d is distance. This equation assumes that the force and distance are constant over time.

3. What is the significance of work done as a function of time?

Work done as a function of time is significant because it allows us to measure and understand the amount of energy required to perform a task or accomplish a goal. It is also a key factor in determining efficiency and productivity.

4. How does work done as a function of time relate to power?

Power is the rate at which work is done, so work done as a function of time is directly related to power. The more work done in a given time period, the higher the power output.

5. Can work done as a function of time be negative?

Yes, work done as a function of time can be negative. This occurs when the force and displacement are in opposite directions, resulting in a negative value for work. It can also happen when work is being done against a resistive force, such as friction, which decreases the overall work done.

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