[sarubobo28]

What is the minimum amount of energy I would need to expend if I were to go to a room 3m to my left and 4m above if I weigh 60kg?

Would it just be 240g? Thanks!

[sarubobo28]

Anyone?

[john !!]

Are you in the same class as this poster?

http://www.thestudentroom.co.uk/show....php?t=1083791

[George the Soapy]

I'm really struggling with this the height part is easy, E = mgh, but I can't figure out how to apply any formula to the horizontal movement... I'm doing Advanced Higher, I should probably be able to do this...

[Boristhethird]

firstly, energy is mesured in Newtons Joules, not grams,
secondly, how much friction/resistance is there on you?
thirdley, do we assume gravaty is 10?

[Smeh]

You need the work done for the horizontal component so like Boristhethird said what is the friction/resistance on you? You work out the work done add that to 240g and badabingbadaboom.
...I think.
Correct me if i'm wrong i'm intrigued now.

[Chike_Obi_soulman]

And No, energy is measured in Joules.
Simply consider Kinetic energy when walking horizontally and potential(vertically).

[SahilB91]

Is it not a case of working out kinetic energy for movement left, then potential energy upwards. Then create a right-angled triangle and use phythagoras' to work out the hypotenuse which is equivalent to the total eneryg required.

[Smeh]

To the guys who said use KE that's what I thought but then I realised we don't have the speed at which she's moving.
Unless the question gives the speed.
Then yes that would be right.

[SahilB91]

assume your speed left is like 1 m/s

KE = 0.5 x 60 x 1^2 = 30 J

then movement up

PE = 60 x g x 4 = 240g J

30^2 + (240g)^2 = hypotenuse


ALTHOUGH it could be a case of adding the two, which doesn't make sense in my mind for some reason

[sarubobo28]

Originally Posted by Boristhethird

firstly, energy is mesured in Newtons, not grams,
secondly, how much friction/resistance is there on you?

Energy is measured in Joules, and g=acceleration of freefall.

There's no info on friction/resistance that's the problem

Originally Posted by Chike_Obi_soulman

Simply consider Kinetic energy when walking horizontally and potential(vertically).

That's what I thought, so I did mgh=240g for vertical and 0.5mv^2 for horizontal but that I thought that could negligible when I travel reaalllyy slow, close to zero, which sounds rediculous but it's minimum energy I need to expend afterall?

[skipp]

Originally Posted by Boristhethird

firstly, energy is mesured in Newtons, not grams,
secondly, how much friction/resistance is there on you?
thirdley, do we assume gravaty is 10?

Think you got your words muddled up there, energy is measured in Joules, Force is measured in Newtons

Mass: kilograms
Force (for example weight): Newtons
Energy: Joules

OP have you been studying the work-energy principle?

[Ramble]

You don't have enough info for the horizontal component so it's probably a trick. Ignore it.
Just work out the vertical.

[sarubobo28]

Originally Posted by SahilB91

assume your speed left is like 1 m/s

KE = 0.5 x 60 x 1^2 = 30 J

then movement up

PE = 60 x g x 4 = 240g J

30^2 + (240g)^2 = hypotenuse


ALTHOUGH it could be a case of adding the two, which doesn't make sense in my mind for some reason

But then I could get across 3m by travelling 0.000000000001m/s (it's the minimum energy I need to expend I'm trying to find) so I would eventually get there but the KE for travelling horizontally would be so small that it can be said as zero?

[Chike_Obi_soulman]

The answer doesn't have to be a fixed value. The easiest path is to consider the "hypothenus". The answer doesn't have to be a value, does it? You can write it in terms of velocity, e.t.c

[sarubobo28]

Originally Posted by john !!

Are you in the same class as this poster?

http://www.thestudentroom.co.uk/show....php?t=1083791

It's one of the oxford admissions questions actually, worth one mark

[Boristhethird]

Originally Posted by skipp

Think you got your words muddled up there, energy is measured in Joules, Force is measured in Newtons

Mass: kilograms
Force (for example weight): Newtons
Energy: Joules

OP have you been studying the work-energy principle?

whoopsie! there was me trying to be all clever and all...

[SahilB91]

Originally Posted by sarubobo28

But then I could get across 3m by travelling 0.000000000001m/s (it's the minimum energy I need to expend I'm trying to find) so I would eventually get there but the KE for travelling horizontally would be so small that it can be said as zero?

I just read it is an Oxford question. The minimum eneryg bit is obviously important as thefore KE -> 0 as you say

In all likeliness you have identified the cheap tricks that Oxford use like pimps in the credit crunch.

I think you are right and therefore only potential matters.

[sarubobo28]

Originally Posted by Chike_Obi_soulman

The answer doesn't have to be a fixed value. The easiest path is to consider the "hypothenus". The answer doesn't have to be a value, does it? You can write it in terms of velocity, e.t.c

Sorry it's actually multiple choice:
a. 1800J
b. 2400J
c. 3000J
d. 4200J
(taking gravitational field strength=10)

But I just wanted to know if there was a proper way of calculating it. I guess it's 2400J then?

[sarubobo28]

Thanks for helping me guys love ya