What is the required wattage to achieve a velocity of 300m/s with 1kg of mass?

[BilPrestonEsq]

How many watts of power would it take to get a a mass of 1kg up to 300m/s? Leaving out friction, drag, etc.. Just how much power in watts to get 1kg to 300m/s. ??

 

[Sourabh N]

Your question seems incomplete. Any amount of power can make a 1kg body move at 300m/s, given enough time.

 

[russ_watters]

...and have you tried using Newton's equations of motion?

 

[BilPrestonEsq]

Doesn't it take the same amount of power to move an object with the mass of 1kg 300m/s regardless of the time it takes? If it took .5 seconds or a year wouldn't it be the same amount of power just over a longer period of time? And yes Newtons laws of motion... I guess that's what I am having trouble with, finding a clear answer to this question. Oh yea and a watt being V*A and an amp being 1 coulomb per*wait* an amp is 1 coulomb passing a GIVEN POINT each second. What does that mean exactly? Arrghh...Man this stuff can get a confusing especially when your biggest teacher is wikipedia.. Help me Physics Forum your my only hope...

 

[kloptok]

Watts are joules per second (power=energy/time). Therefore we need to know for how long time the power is applied in order to know the answer to your question.

Doesn't it take the same amount of power to move an object with the mass of 1kg 300m/s regardless of the time it takes? If it took .5 seconds or a year wouldn't it be the same amount of power just over a longer period of time?

No. If it took .5 seconds the power would be 90 kW, if it took a year the power would be about 1.4 mW, assuming constant power and no initial velocity.

I think you're maybe mixing up energy and power? The energy needed to accelerate the object to 300 m/s would be 45 kJ in both cases.

 

[BilPrestonEsq]

Oh 90kw is actually what I got at first and I thought it was wrong. Thanks

 

[BilPrestonEsq]

How is it though that it would take 1.4mw if it is the same energy? That sounds like a lot more energy to me. Isn't that that same as lifting 100lbs in one second compared to lifting in 1min using a pulley. Same energy is used, 90kw vs. 1.4mw doesn't make much sense to me. What equations did you use to find that number? I know I could find it someplace else but I wouldn't be sure I had it right and that's why I joined PF. I appreciate the help.

 

[kloptok]

You're mixing up energy and power. The same energy, 45000 Joules, is used in both cases (here i simply used that energy is equal to 0.5*m*v²), but the (average) power is NOT the same!

If the mass is accelerated in .5 seconds, the average power is P = 45000 J / 0.5 s = 90000 W.

If the mass is accelerated in one year, the average power is (60*60*24*365=31536000 seconds in one year) P = 45000 J / 31536000 s = 0.0014 W.

You have to realize that power is a measure of energy per time, not a measure of energy. Therefore the power needed depends on the time the power is applied.

 

[K^2]

Listen to kloptok. Also, keep in mind that colloquial meanings of some words are completely different from what they mean in physics. Always check definitions of actual terms.

 

[BilPrestonEsq]

to kloptok I thought you meant 1.4 megawatts .0014watts makes a lot more sense. Thank you guys for answering my stupid questions I am very new to this stuff.

 

[kloptok]

No no, the prefix m stands for 'milli', 10^-3. The prefix for 'mega',10⁶, is a capital M.

Don't be afraid to ask questions, as the saying goes: "There are no stupid questions, only stupid answers".