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Finding this GCSE physics Question really hard - please help

A ball of mass 0.5 kg is thrown directly up with a speed of 6ms-1. Calculate:

(1) Its maximum gain in potential energy

(2) The maximum height gained
(edited 8 years ago)
Reply 1
Anyone please?
Original post by Sam00
A ball of mass 0.5 kgis thrown directly up with a speed of 6ms-1. Calculate:

(1) Its maximum gain in potential energy

(2) The maximum height gained


here you could use conservation of energy... KE of ball at launch = mgh

suvat is also a possibility for part 2 - you should find it doesn't contradict the result of your conservation of energy calculation :smile:
Reply 3
Original post by Joinedup
here you could use conservation of energy... KE of ball at launch = mgh

suvat is also a possibility for part 2 - you should find it doesn't contradict the result of your conservation of energy calculation :smile:


So do I need to work out part 2 before I can work out part 1?
Original post by Sam00
A ball of mass 0.5 kg is thrown directly up with a speed of 6ms-1. Calculate:

(1) Its maximum gain in potential energy

(2) The maximum height gained


Gain in potential energy = loss in Kinetic energy

So just work out kinetic energy for part (1)

Second part...well I do A-level Physics & would use SUVAT, if you do that in GCSE do SUVAT at v=0 lol
Reply 5
Original post by KINGYusuf
Gain in potential energy = loss in Kinetic energy

So just work out kinetic energy for part (1)

Second part...well I do A-level Physics & would use SUVAT, if you do that in GCSE do SUVAT at v=0 lol


Or for part 2 you could use the formula for graviaitonal potential energy, and the answer to part one, and rearrange for height.
Original post by Sam00
So do I need to work out part 2 before I can work out part 1?


No, you need to do part 1 first. One way of doing part 2 follows directly from part 1 though.
Reply 7
Original post by KINGYusuf
Gain in potential energy = loss in Kinetic energy

So just work out kinetic energy for part (1)

Second part...well I do A-level Physics & would use SUVAT, if you do that in GCSE do SUVAT at v=0 lol


I have an exam tomorrow and I'm panicking,

So for part 1 the answer is 9J but I need to learn to method used to get the 9J?

This is what I don't understand, however if I knew the height I would be able to work out the first question?!?!
Reply 8
Original post by Sam00
I have an exam tomorrow and I'm panicking,

So for part 1 the answer is 9J but I need to learn to method used to get the 9J?

This is what I don't understand, however if I knew the height I would be able to work out the first question?!?!


kinetic energy = 12 × mass × velocity2
Original post by Sam00
I have an exam tomorrow and I'm panicking,

So for part 1 the answer is 9J but I need to learn to method used to get the 9J?

This is what I don't understand, however if I knew the height I would be able to work out the first question?!?!



REMEMBER THIS WITH YOUR LIFE & YOU WILL SUCCEED:

LOSS OF GPE = GAIN IN KE

GPE = mgh
KE = 1/2mv^2

so mgh = 1/2mv^2

So they gave you mass & velocity, you can work out the kinetic energy as you know kinetic energy is = to potential energy
Original post by Sam00
I have an exam tomorrow and I'm panicking,

So for part 1 the answer is 9J but I need to learn to method used to get the 9J?

This is what I don't understand, however if I knew the height I would be able to work out the first question?!?!


throwing a ball straight up in the air starts an energy conversion process.

on the way up it's converting KE to GPE and on the way down it's converting GPE back to KE. The peak value of GPE occurs when KE=0 and KE equals zero when it's velocity is zero.

the maximum efficiency of an energy conversion is 100%... so part 1 is just asking you to find the value of h at which mgh=1/2 m v2

you already know m,g & v so it shouldn't be too difficult.
Reply 11
Original post by Joinedup
throwing a ball straight up in the air starts an energy conversion process.

on the way up it's converting KE to GPE and on the way down it's converting GPE back to KE. The peak value of GPE occurs when KE=0 and KE equals zero when it's velocity is zero.

the maximum efficiency of an energy conversion is 100%... so part 1 is just asking you to find the value of h at which mgh=1/2 m v2

you already know m,g & v so it shouldn't be too difficult.


ok now the first part makes sense, 0.5(0.5x6^2) = 9J

I will now attempt the second part
Reply 12
Original post by KINGYusuf
REMEMBER THIS WITH YOUR LIFE & YOU WILL SUCCEED:

LOSS OF GPE = GAIN IN KE

GPE = mgh
KE = 1/2mv^2

so mgh = 1/2mv^2

So they gave you mass & velocity, you can work out the kinetic energy as you know kinetic energy is = to potential energy

I've worked out part 1 but need to do part 2 using SUVAT?

Still not sure :frown:

And thanks rep given
Original post by Sam00
I've worked out part 1 but need to do part 2 using SUVAT?

Still not sure :frown:

And thanks rep given


Have you done SUVAT? If you haven't, don't worry.

You can use the LOSS OF POTENTIAL ENERGY = GAIN IN KINETIC ENERGY formula

So mgh = 1/2mv^2

Plot in your values & find h, the height :biggrin:!
Reply 14
Original post by KINGYusuf
Have you done SUVAT? If you haven't, don't worry.

You can use the LOSS OF POTENTIAL ENERGY = GAIN IN KINETIC ENERGY formula

So mgh = 1/2mv^2

Plot in your values & find h, the height :biggrin:!


I am sorry I don't follow
Original post by Sam00
I am sorry I don't follow




You know loss in potential energy = gain in kinetic energy

Since (gravitational) potential energy = mgh

& kinetic energy = 1/2mv^2

you can equate them together since they are equal

so mgh = 1/2mv^2

m = mass
g= gravitational field strength
h = height
v= velocity

So they gave you mass & velocity. Now rearrage mgh = 1/2mv^2 to make the height, h the subject & subtitute the values given
Reply 16
Original post by KINGYusuf
You know loss in potential energy = gain in kinetic energy

Since (gravitational) potential energy = mgh

& kinetic energy = 1/2mv^2

you can equate them together since they are equal

so mgh = 1/2mv^2

m = mass
g= gravitational field strength
h = height
v= velocity

So they gave you mass & velocity. Now rearrage mgh = 1/2mv^2 to make the height, h the subject & subtitute the values given


0.5 x 9.81 x h = 9J
0.5(0.5 x 6^2) = 9J

h = 9/0.5x9.81

h = 1.83

Thank you kind sir
Original post by Sam00
A ball of mass 0.5 kg is thrown directly up with a speed of 6ms-1. Calculate:
(1) Its maximum gain in potential energy
(2) The maximum height gained
Right-o
Original post by Sam00
I have an exam tomorrow and I'm panicking,
So for part 1 the answer is 9J but I need to learn to method used to get the 9J?
This is what I don't understand, however if I knew the height I would be able to work out the first question?!?!
How did the exam go?
Original post by Sam00
ok now the first part makes sense, 0.5(0.5x6^2) = 9J
I will now attempt the second part
Jolly Good
Original post by Sam00
0.5 x 9.81 x h = 9J
0.5(0.5 x 6^2) = 9J
h = 9/0.5x9.81
h = 1.83
Thank you kind sir
Splendid, time to close the thread one thinks.
Height is calculated using the GPE equation. Assuming you have calculated gain in potential energy in part 1, rearrange Ep = mgh to height = potential energy / (mass * 9.81)
Original post by 04MR17
Splendid, time to close the thread one thinks.
Damn. I was way too cocky four years ago.

Original post by AndrewMarriott3
Height is calculated using the GPE equation. Assuming you have calculated gain in potential energy in part 1, rearrange Ep = mgh to height = potential energy / (mass * 9.81)
I would think that four years later OP has worked it out by now. :wink:

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