Trying to understand power/work

  • Thread starter southernson
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In summary, power in the horizontal direction makes less sense to me. If a tractor has twice the power it can similarly do twice the work in the same time, but can it pull the same mass from point A to B in half the time? If you look at power as KEf-KEi/t, it would appear that it can't because velocity is squared in the KE equation (KE = 1/2mv^2).
  • #1
southernson
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you see a lot of reference to the fact that a forklift or winch or something with "twice" the power of a another one can lift twice the mass in the same time, or the same mass in half the time, etc. This makes sense.

Power in the horizontal direction makes less sense to me. If a tractor has twice the power it can similarly do twice the work in the same time, but can it pull the same mass from point A to B in half the time? If you look at power as KEf-KEi/t, it would appear that it can't because velocity is squared in the KE equation (KE = 1/2mv^2).

Can someone help me clarify this?
 
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  • #2
southernson said:
you see a lot of reference to the fact that a forklift or winch or something with "twice" the power of a another one can lift twice the mass in the same time, or the same mass in half the time, etc. This makes sense.

Power in the horizontal direction makes less sense to me. If a tractor has twice the power it can similarly do twice the work in the same time, but can it pull the same mass from point A to B in half the time? If you look at power as KEf-KEi/t, it would appear that it can't because velocity is squared in the KE equation (KE = 1/2mv^2).

Can someone help me clarify this?

Well, tractors don't pull at the same power regardless of speed. But if they they did then I guess the velocity of the tractor would increase quadratically (assuming no friction).
 
  • #3
Tractors are normally pulling against a constant load, not acceleration. Power equals force times speed, so a tractor with double the power will be able to pull the same load (tension force) at twice the speed.

In the case of acceleration with a constant mass, since the change in energy is relative to 1/2 m V^2, then twice the power only increases the rate of acceleration by SQRT(2) (with the same mass), and it takes 4 times the power to double the rate of acceleration (or think of 4 times the power as twice as much force at twice as much speed with constant acceleration).
 
  • #4
Sorry guys, I'm still confused. Let's use a different example. Say just a car with an engine of power P and another with a power of 2P. If the first can go 0 to 60m/s in 20 seconds can the second to it in 10 seconds? If so, this can only happen by the second engine causing a faster acceleartion. How is that going to happen without a greater force?
 

1. What is the definition of power?

Power is the ability to influence or control others, resources, or events. It can also refer to the amount of work done in a given amount of time.

2. How is power measured?

Power can be measured in watts, which is equal to one joule per second. It can also be measured in horsepower, which is approximately 746 watts.

3. What is the relationship between power and work?

Work is defined as the application of force over a distance. Power is the rate at which work is done. Therefore, the more power that is exerted, the more work can be accomplished in a given amount of time.

4. Can power be created or destroyed?

No, according to the Law of Conservation of Energy, energy cannot be created or destroyed. So, while power can be transferred or converted from one form to another, it cannot be created or destroyed.

5. How does one gain or increase power?

There are several ways to gain or increase power, including acquiring resources, building relationships and alliances, developing expertise and skills, and demonstrating strong leadership and decision-making abilities.

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