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# Gcse physics question help

Need help with the explanation part of this question
A group of friends go sliding down a water slide seperately, they sit on a sled and go down the slide.
The decrease in gravitational potential energy of one rider on the slide was7.66kJ, the rider moved through a verticle height of 16.0M with a gravitational field of 9.8 N/Kg

at the bottom of the slide, all the friends and their sleds have approximately the same speed. why? (4 Marks)
Original post by shaheryar9
Need help with the explanation part of this question
A group of friends go sliding down a water slide seperately, they sit on a sled and go down the slide.
The decrease in gravitational potential energy of one rider on the slide was7.66kJ, the rider moved through a verticle height of 16.0M with a gravitational field of 9.8 N/Kg

at the bottom of the slide, all the friends and their sleds have approximately the same speed. why? (4 Marks)

omg i had this in my physics exam a few weeks ago, i literally had no clue what to write
sorry lol
I need help with this too! Does someone know how to answer this?
bumppp
Damn this is hard. Maybe you have to talk about the energy transfers? It changes from gravitational potential to kinetic potential, so because the height they travel down is the same, the speed would also be the same. They question mentions numbers so I guess we’re also going to have to do a calculation.
This ones got me stumped...
(edited 2 years ago)
I might be wrong but is it to do with the fact that their total weight balances with the air resistance/friction they experience (initially they were accelerating because weight was larger than air resistance), so their terminal speed is the same. It seems like a reasonable answer...
You could say
They all have the same speed because they travel the same distance as the height of the slide is 16M. There is no friction as the slide is a water slide and water acts as a lubricant, so they aren’t affected by friction. At the top of the slide the gravitational energy is acting on them, but as they move the energy transfers to the stored kinetic energy, so the energy is from the kinetic energy store aswell. As they reach the end they reach their maximum kinetic potential.
I might just be waffling but this is the best answer I got.
as it's the same slide for every rider, the slide is the same height for every rider which means they must have the same amount of gravitational potential energy store. this means when they are released, they will travel down the slide at different rates due to their differences in mass but the maximum kinetic energy will be the same as the gravitational potenital energy store at the start of the slide so all riders can only reach a maximum speed. hope this helps
Sorry for the useless and late response - but if any of your are still curious or plan on doing A-Level at physics i hope this helps .
I remember the first part of the question asking you to recall E=mgh to calculate the energy.

E= mgh
E=1/2mv^2
therefore mgh = 1/2mv^2
if you divide m from both sides you get gh =1/2v^2
since the height and gravity are constant the velocity will always be the same - you can work it out but you dont have to since it only asks you to explain and i got full marks.

p.s. '' ^2 '' means squared
Original post by T0bu
Sorry for the useless and late response - but if any of your are still curious or plan on doing A-Level at physics i hope this helps .
I remember the first part of the question asking you to recall E=mgh to calculate the energy.

E= mgh
E=1/2mv^2
therefore mgh = 1/2mv^2
if you divide m from both sides you get gh =1/2v^2
since the height and gravity are constant the velocity will always be the same - you can work it out but you dont have to since it only asks you to explain and i got full marks.

p.s. '' ^2 '' means squared

This is what I wrote in the mock. Can you tell me how many marks out of four I might get for this:
Ep= m x g x h
Ep=Ek
Ek= 1/2 x m x v^2
v=squareroot(Ek/0.5 x m)
Even if the mass is changed the velocity stays the same
eg.
50 kg x 9.8 x 20=9800 J
squareroot(9800/ 0.5 x 50)=19.8 m/s

70 kg x 9.8 x 20=13720 J
squareroot(13720/0.5 x 70)=19.8 m/s
Original post by Murdered Potato
This is what I wrote in the mock. Can you tell me how many marks out of four I might get for this:
Ep= m x g x h
Ep=Ek
Ek= 1/2 x m x v^2
v=squareroot(Ek/0.5 x m)
Even if the mass is changed the velocity stays the same
eg.
50 kg x 9.8 x 20=9800 J
squareroot(9800/ 0.5 x 50)=19.8 m/s

70 kg x 9.8 x 20=13720 J
squareroot(13720/0.5 x 70)=19.8 m/s

I previously answered this questions when I was doing GCSE and I couldn’t crack it. Now that I’m doing A level physics I’ve finally worked it out, and it’s the same as yours I believe.

The gravitational potential energy store decreases as they move down.
This store changes to kinetic, so Ep=Ek
0.5xmxv^2=mgh
Rearrange to get v=root(2gh) Mass cancels out
So they all have the same velocity as they travelling down the same vertical height at the acceleration of free fall (because of no air resistance).

I believe you’ve got it right
thank u i copied this down word for word 😊