
#1
Nov2408, 08:37 PM

P: 7

A constant direction force delivers a constant power of 45.0 W to an 8.00kg 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. 



#2
Nov2408, 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? 



#3
Nov2408, 10:10 PM

P: 7

Kg m^2/s^3
Few more points would be helpful. Thanks 



#4
Nov2408, 10:44 PM

HW Helper
P: 5,346

Constant Power
OK and how is power related to Force?
Power = Force times ...? 



#5
Nov2408, 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)




#6
Nov2408, 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? 



#7
Nov2508, 04:12 PM

P: 7

Ahh thanks alot man.. appreciate it.



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