Gen question about work-energy principle

AI Thread Summary
The discussion revolves around the work-energy principle as it applies to a truck driving up a slope. The original formula presented for calculating the total work done by the truck's engine was incorrect; it should account for the gain in potential energy (PE) and the work done against friction, while recognizing that the loss in kinetic energy (KE) should be treated as negative. This reflects the conversion of kinetic energy into potential energy during the ascent. The clarification provided helps solidify the understanding of energy conservation in this context. The user expresses gratitude for the timely assistance before finals.
Boogeyman
Messages
75
Reaction score
0
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 postive. Is it the magnitude I'm considering?
 
Physics news on Phys.org
Hi Boogeyman!

Boogeyman said:
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 postive. 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.)
 
I like Serena said:
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.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Egg Drop Challenge! Need ideas for winning designs'

I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
View full post »

Similar threads

Work & Energy (Question on Classical Mechanics/Slope based Problems)
Replies
7
Views
2K
About KE and PE of a stone falling down a tube filled with oil
Replies
10
Views
2K
Help with the work-energy principle
Replies
10
Views
3K
D’Alembert Vs Conservation of Energy
Replies
3
Views
5K
About work done through exercise (push ups)
Replies
4
Views
3K
Very quick question regarding work and kinetic energy
Replies
1
Views
1K
Work and kinetic energy comprehension question
Replies
4
Views
2K
Not sure how to plug in numbers for Work Energy Theorem
Replies
13
Views
3K
Why Is Work Positive When Done Against the Electric Field?
Replies
22
Views
3K
How Can D'Alembert's Principle Help Solve This Problem?
Replies
6
Views
2K

Hot Threads

Recent Insights

Back
Top