Calculating Speed of Mass Given Constant Power & Force

[Fluent]

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 a lot of steps.

Thanks.

 

[LowlyPion]

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]

Kg m^2/s^3

Few more points would be helpful.

Thanks

 

[LowlyPion]

OK and how is power related to Force?

Power = Force times ...?

 

[Fluent]

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]

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]

Ahh thanks a lot man.. appreciate it.