SweetCupcake
Well-known member
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Can anyone help with physics assignment?
- Thread starter SweetCupcake
- Start date
DanFC
Well-known member
Well, I hate physics, but I have to study it anyways for the MCAT (why!?!?) 
Is this a quick thing/problem or is it longer? If the latter, I'll be available all day tomorrow, but I've got to run experiments in an hour which will go through the night.
By the way, I know one of our other members is a graduating engineer, I'm sure he can help much more than myself ^_^
Is this a quick thing/problem or is it longer? If the latter, I'll be available all day tomorrow, but I've got to run experiments in an hour which will go through the night.
By the way, I know one of our other members is a graduating engineer, I'm sure he can help much more than myself ^_^
SweetCupcake
Well-known member
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DanFC
Well-known member
Okay, it's been a while so I don't know if it's right, but I think v(f) = 11.37.
I think it's just conversation of energy, and since there's no friction, KE(i) + U(i) = KE(f) + U(f) where KE = kinetic energy, U = potential energy, i = initial, and f = final. Putting in the numbers and given that there's no potential energy in (f) because it's at a height of 0, KE = 1/2mv^2, PE = mgh:
(1/2)(m)(9.7)^2 + m(9.8)(1.8) = (1/2)(m)(v(f))^2 + 0
All of the m's cancel out, and you can solve for v(f). You should probably double check my method/work though, since I'm generally bad at physics
I think it's just conversation of energy, and since there's no friction, KE(i) + U(i) = KE(f) + U(f) where KE = kinetic energy, U = potential energy, i = initial, and f = final. Putting in the numbers and given that there's no potential energy in (f) because it's at a height of 0, KE = 1/2mv^2, PE = mgh:
(1/2)(m)(9.7)^2 + m(9.8)(1.8) = (1/2)(m)(v(f))^2 + 0
All of the m's cancel out, and you can solve for v(f). You should probably double check my method/work though, since I'm generally bad at physics
SweetCupcake
Well-known member
Eat cheeseeeeeeeeeeeeeeeeee
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DanFC
Well-known member
No problem. By the way, next time you might want to put it in the Science Help thread. You might get more responses that way since that's what the thread's for. I'd be happy to help again
Edit: Regardless Dronee, I don't know if the link would've helped. I don't see how the problem could be solved by projectile motion, did I miss something?
Edit: Regardless Dronee, I don't know if the link would've helped. I don't see how the problem could be solved by projectile motion, did I miss something?
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Dronee
1
No problem. By the way, next time you might want to put it in the Science Help thread. You might get more responses that way since that's what the thread's for. I'd be happy to help again
Edit: Regardless Dronee, I don't know if the link would've helped. I don't see how the problem could be solved by projectile motion, did I miss something?
I used pure math approach. I thought that by symmetry, the time when it returned back to the place it started... it should go downwards at a speed of 9.7m/s. Then take that as initial speed...
So the problem is restated as the woman throws the ball downwards at a speed of 9.7m/s from a height of 1.8 m. Then simply plug in the values. By using the formula for simple integration you'll get...
(Lazy to type or copy)
Overview of Gravity Equation Derivations by Ron Kurtus - Succeed in Understanding Physics: School for Champions
Plug in the formula from the above and everything nicely works out to the square root of vi (square) + 2
(g).. where vi is the initial velocity. I got 11.37409. But then again, I almost never took physics beyond first parts of high school. So I could be wrong... though it'll be quite a coincidence how I got the answer.
Edit: Hmm... think I only used the v =... formula.
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SweetCupcake
Well-known member
Thanks. This is probably a stupid question but was does the ^ mean?
DanFC
Well-known member
I used pure math approach. I thought that by symmetry, the time when it returned back to the place it started... it should go downwards at a speed of 9.7m/s. Then take that as initial speed...
So the problem is restated as the woman throws the ball downwards at a speed of 9.7m/s from a height of 1.8 m. Then simply plug in the values. By using the formula for simple integration you'll get...
(Lazy to type or copy)
Overview of Gravity Equation Derivations by Ron Kurtus - Succeed in Understanding Physics: School for Champions
Plug in the formula from the above and everything nicely works out to the square root of vi (square) + 2
I got 11.37409. But then again, I almost never took physics beyond first parts of high school. So I could be wrong... though it'll be quite a coincidence how I got the answer.
Edit: Hmm... think I only used the v =... formula.
And that's why I hate physics, it's requires a way of thinking I can never wrap my head around XD
And I used ^ in my explanation as power: ^2 is squared, ^3 is cubed.
Dronee
1
I think it means power. E.g: 4^2 = 16
You may want to double check this... But I believe that you can just use v = ±√(2gy + vi^2)... for all questions of this exact type if it's a math question. And use DanFC method when this kind of question appears as a physics question
Edit: I'm not good at physics either. I think it's interesting, but lol... I suck at it. Come to think of it, Maths is sometimes tough too. I remember this nice lecturer/prof once taught a course in 'elementary logic'. He argued his way into 'logically' convincing us that all horses were blue. And we found NO loopholes in his arguments at first. The lecture almost turned into a riot as the students were either laughing, furiously thinking or suffering from mental strain... lol... Anyway, sorry to derail the thread. Just reminiscing.
You may want to double check this... But I believe that you can just use v = ±√(2gy + vi^2)... for all questions of this exact type if it's a math question. And use DanFC method when this kind of question appears as a physics question
Edit: I'm not good at physics either. I think it's interesting, but lol... I suck at it. Come to think of it, Maths is sometimes tough too. I remember this nice lecturer/prof once taught a course in 'elementary logic'. He argued his way into 'logically' convincing us that all horses were blue. And we found NO loopholes in his arguments at first. The lecture almost turned into a riot as the students were either laughing, furiously thinking or suffering from mental strain... lol... Anyway, sorry to derail the thread. Just reminiscing.
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