Gen question about work-energy principle

[Boogeyman]

Hello, I am confused about this concept. Say, a truck drives up a slope. It decelerates as it ascends. I am required to find the total work done by the engine of the truck, and I know this to be:

Work done=Gain in PE + Loss in KE + Work done against friction

However I'm unsure whether the the loss in KE is negative or positive. Is it the magnitude I'm considering?

 

[I like Serena]

Hi Boogeyman!

Hello, I am confused about this concept. Say, a truck drives up a slope. It decelerates as it ascends. I am required to find the total work done by the engine of the truck, and I know this to be:

Work done=Gain in PE + Loss in KE + Work done against friction

However I'm unsure whether the the loss in KE is negative or positive. Is it the magnitude I'm considering?

Your formula is off. It should read:

Work done=Gain in PE + Gain in KE + Work done against friction​

Since your losing KE it will come out negative in the formula.This should fit the intuitive sense of energy conversions and conservation of energy.
(Kinetic energy is converted to potential energy, canceling out in the work-done formula.)

 

[Boogeyman]

Hi Boogeyman!



Your formula is off. It should read:

Work done=Gain in PE + Gain in KE + Work done against friction​

Since your losing KE it will come out negative in the formula.


This should fit the intuitive sense of energy conversions and conservation of energy.
(Kinetic energy is converted to potential energy, canceling out in the work-done formula.)

Oh man thanks a bunch I have finals tomorrow and this was the only thing that was gray in my mind.