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Physics - Energy

I really don't understand this question, help, please!!

A car of mass 1,000 kg begins stationary on a road at the top of a mountain, at a height h = 3,000 m. The car then rolls freely down a winding road, travelling a total distance of 5 km, to reach the height h = 2,000 m. Assume g = 9.8 ms-2:

How much energy did the car lose on descent? Give you answer to 3 significant figures, with units.

The answer is: 9,800,000 J

but I just don't get it.
Okay its like a little bit of trick question bear with

As something is held at a height it has gravitational potential energy right, and then as it falls this is transferred into kinetic energy. In this case some energy has been lost because if the energy had been completely transferred the car would have gone up 3000km on the other side but it only reached 2000km. Losing 1000km of height

Using mgh as energy you should be able to solve the question. I don't want to give you the answer so its a little cryptic ik but if you need it explained more lmk
Original post by Roasted Potato
Okay its like a little bit of trick question bear with

As something is held at a height it has gravitational potential energy right, and then as it falls this is transferred into kinetic energy. In this case some energy has been lost because if the energy had been completely transferred the car would have gone up 3000km on the other side but it only reached 2000km. Losing 1000km of height

Using mgh as energy you should be able to solve the question. I don't want to give you the answer so its a little cryptic ik but if you need it explained more lmk

Its not a trick question


@16uahmed
Its a simple energy question, all you need to know is how to calculate potential energy, and find the numbers from the question.
This might help
E = mg∆h
(edited 3 years ago)
Original post by mnot
Its not a trick question


@16uahmed
Its a simple energy question, all you need to know is how to calculate potential energy, and find the numbers from the question.

The first thing I thought was a SUVAT problem and if like me you get super into the maths and don't always read a question properly it feels like a trick question as it is perceived harder than it actually is using SUVAT would be very hard and not necessary. Its just my opinion tbh, no hatin'
Original post by Roasted Potato
Okay its like a little bit of trick question bear with

As something is held at a height it has gravitational potential energy right, and then as it falls this is transferred into kinetic energy. In this case some energy has been lost because if the energy had been completely transferred the car would have gone up 3000km on the other side but it only reached 2000km. Losing 1000km of height

Using mgh as energy you should be able to solve the question. I don't want to give you the answer so its a little cryptic ik but if you need it explained more lmk


Your right about it being cryptic.
Why the **** do they need so many words


Most people dont realise its E =m•g•∆h , I dont know why they teach E = mgh .
(edited 3 years ago)
Reply 6
Original post by mnot
Its not a trick question


@16uahmed
Its a simple energy question, all you need to know is how to calculate potential energy, and find the numbers from the question.

thanks :biggrin:
Original post by Owenstampy
Your right about it being cryptic.
Why the **** do they need so many words


Most people dont realise its E =m•g•∆h most , I dont know why they teach E = mgh .

Its about getting people to recognise what the problem is, if it was just E= mgh it would be a primary school multiplication problem, the fact they can ask you any number of mechanics based principles and you have to think critically about what principle to apply is what makes it a more complex problem.
The equation for g.p.e is gpe = change in height x mass x gravitational field strength,as the change in height goes from 3000 to 2000, the difference is 1000 making the change in height being 1000the mass is 1000 kg as clearly stated in the questionand gravitational field strength is 9.8 ms^-2 as once again clearly stated in the questio***** we found these values, we slot in the numbers in the equation looking like

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