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### Topic: Kinetic Energy problem  (Read 4497 times)

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#### Zanelias

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##### Kinetic Energy problem
« on: May 28, 2014, 12:20:32 PM »
A vehicle of mass 2.8 t slows from 100. km*h^-1 to 50. km*h^-1 as it enters the city. How much energy could have been recovered, instead of dissipated as heat? To what height, neglecting friction and other losses, could that energy have been used to drive the vehicle up a hill?

The answer is 4.0x10^3 kJ, and 150 m for the second part, but I don't know how they got either. It's a standard kinetic and potential energy problem. Ek=.5*mass*speed, Ep=kg*speed*9.81"acceleration of gravity". Sorry if this seems like a dumb question, but I'm just a beginner, so any help is appreciated.

#### Borek

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##### Re: Kinetic Energy problem
« Reply #1 on: May 28, 2014, 02:05:20 PM »
Hardly chemistry, moving it to other sciences.

Ek=.5*mass*speed, Ep=kg*speed*9.81"acceleration of gravity"

None of these formulas look OK.
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#### Zanelias

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##### Re: Kinetic Energy problem
« Reply #2 on: May 31, 2014, 01:32:17 PM »
The problems one of the intro problems from my Atkins book, sorry about the topicality issue. The formulas are also from the book, what seems to be wrong with them?