Kinetic Energy Vs. Potential Energy confusion.

AI Thread Summary
The discussion revolves around a physics problem involving a car's deceleration and the work done to stop it. The participant is uncertain about applying the Conservation of Energy principle to the scenario. They are prompted to calculate the car's initial speed to determine the work done in stopping. The conversation indicates a shift in focus as the participant realizes they may have started a new thread inadvertently. The importance of understanding kinetic and potential energy in this context is emphasized.
teriblekelly
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Homework Statement



A car and driver weighing 5530 N passes a
sign stating \Bridge Out 25:5 m Ahead." She
slams on the brakes, and the car decelerates
at a constant rate of 13:7 m=s2 :
The acceleration of gravity is 9:8 m=s2 :
What is the magnitude of the work done
stopping the car if the car just stops in time
to avoid diving into the water? Answer in
units of J.


Homework Equations


This is where I'm stuck. In class today we learned about Conservation of Energy and I don't know if that applies here.


The Attempt at a Solution

 
Physics news on Phys.org
Yes, Conservation of Energy (COE) applies. Try.
 
Can you find out the speed of the car initially?

From that, what do you think you should calculate?
 
sorry i think i started a new thread by accident can we go to that one? i worked out a few things.
 
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}...
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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.
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