Constant Power


by Fluent
Tags: constant, power
Fluent
Fluent is offline
#1
Nov24-08, 08:37 PM
P: 7
A constant direction force delivers a constant power of 45.0 W to an 8.00-kg mass which is
initially moving in the direction of the force. At t = 0 s, the force is 5.00 N.
Calculate the speed of the mass after 4.00 s.

I've tried to do several different things, however I believe you need to integrate. My intregration skills are really weak, so please don't assume I'll know what you're doing if you skip alot of steps.

Thanks.
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LowlyPion
LowlyPion is offline
#2
Nov24-08, 09:24 PM
HW Helper
P: 5,346
Welcome to PF.

You're in luck. You won't need to integrate.

But you will need to understand what power is.

Like what units is power expressed in?
Fluent
Fluent is offline
#3
Nov24-08, 10:10 PM
P: 7
Kg m^2/s^3

Few more points would be helpful.

Thanks

LowlyPion
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#4
Nov24-08, 10:44 PM
HW Helper
P: 5,346

Constant Power


OK and how is power related to Force?

Power = Force times ...?
Fluent
Fluent is offline
#5
Nov24-08, 11:02 PM
P: 7
velocity.. however unfortunately the answer is not 9 m/s. The other information is needed to solve this.. as the force isn't the same throughout.. (it's 5.00 N only at t = 0 s)
LowlyPion
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#6
Nov24-08, 11:09 PM
HW Helper
P: 5,346
You are jumping ahead a bit.

The 9 m/s is the speed at t=0 however.

Now think about what is a watt? A Joule/sec perhaps?

And how many seconds? So how many Joules were added to the energy of the mass? ...

And how many joules of energy did the mass have at t=0? And added together as Kinetic energy how fast does that mean the mass is going?
Fluent
Fluent is offline
#7
Nov25-08, 04:12 PM
P: 7
Ahh thanks alot man.. appreciate it.


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