Calculating power without distance?

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The discussion centers on calculating the average power developed by a vehicle that accelerates to a speed of 30 m/s over 20 seconds. The kinetic energy (KE) of the vehicle is calculated to be 675,000 joules using the standard formula. Participants clarify that power is the rate of energy change over time, not necessarily dependent on distance. It is suggested that the average power can be found by dividing the kinetic energy by the time interval of 20 seconds. This leads to the conclusion that the average power developed is indeed the kinetic energy divided by the time taken.
fattydq
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So here's my homework problem:

Calculate KE of a 1500 kg vehicle moving at 30 m/2. Which I did, and got 675000 joules, using the standard KE formula.

But then it asks, if the vehicle accelerated to this speed in 20 seconds, what average power was developed?

Any formula for power involves a distance, which is not given here at all. Can someone help me out? Is it a trick question?
 
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fattydq said:
So here's my homework problem:

Calculate KE of a 1500 kg vehicle moving at 30 m/2. Which I did, and got 675000 joules, using the standard KE formula.

But then it asks, if the vehicle accelerated to this speed in 20 seconds, what average power was developed?

Any formula for power involves a distance, which is not given here at all. Can someone help me out? Is it a trick question?

If it acquires its energy in some amount of time, that implies an average power level input during that time interval...
 
As long as the acceleration is constant, the average velocity is the average of the starting and ending velocities. You can use that to find the average kinetic energy.

And I am surprised to hear that "Any formula for power involves a distance". I was under the impression that "power" was "rate of change of energy over time".

(You could, of course, calculate the distance moved at a constant acceleration in a given time. For constant acceleration, a, and time, t, the velocity is at. You can use that to find a from the information given. The distance moved is (1/2)at^2.)
 
Well the reason I thought I needed a distance was because the formula for power is the change in work over the change in time. SOOOO the formula for work is force times DISTANCE. So I don't understand how can I calculate power if I can't find work.
 
fattydq said:
Well the reason I thought I needed a distance was because the formula for power is the change in work over the change in time. SOOOO the formula for work is force times DISTANCE. So I don't understand how can I calculate power if I can't find work.

It's not change in work, it's amount of work (or energy) in some amount of time.
 
berkeman said:
It's not change in work, it's amount of work (or energy) in some amount of time.

So I just divide the numerical answer for kinetic energy by 20?
 
fattydq said:
So I just divide the numerical answer for kinetic energy by 20?

I believe that is correct.
 

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