anybody good at physics?

[ProjectWidow]

anybody here good at physics? LIke the conservation of mechanical energy?

[Hulud]

no if so why would we be here? lol jk

[ProjectWidow]

no if so why would we be here? lol jk
i dunno. I just need to ask a general question about it to help me solve some problems

[ProjectWidow]

somone has to be good here

[D16Civic]

why dont u just ask the question and then someone might be able to help u out
i wouldnt say im good at physics (got a 79 in the last class i took) but i might know it if i see it

[ProjectWidow]

1. A physics book of unknown mass is dropped 4.75 m. What speed does the book have just before it hits the ground? Assume that air resistance is negligible.
____m/s

[soul]

i took ap physics ask away

[imbosile]

i'm in phsyics this year, got a 93 thus far...yea just put the ? up then we can try and figure it out...

[imbosile]

well Potential Energy = mass(gravity)(height), and Kinetic Energy = (.5)(mass)(velocity^2), but i guess that doesnt help to much, lol

[ProjectWidow]

well Potential Energy = mass(gravity)(height), and Kinetic Energy = (.5)(mass)(velocity^2), but i guess that doesnt help to much, lol
i got that far, and I solved for velocity but i need to find Joules

[imbosile]

i thought you said the mass was unkown, how did you get that far without mass?

[imbosile]

why are you looking for joules, when you said you were looking for velocity?

[D16Civic]

isnt that question just asking for velocity, so why do u need to find joules?

[ProjectWidow]

isnt that question just asking for velocity, so why do u need to find joules?
woops, got it confused with a different question

yeh im looking for velocity

[soul]

10m/s * 4.75

[D16Civic]

use this
v^2=V (initial)^2 + 2a(distance)

[ProjectWidow]

10m/s * 4.75
i tried that and it's not the right answer

[imbosile]

i dont know if that would work because in true life things dont actually continuously accelerate at 9.81 m/s.....there is terminal velocity

[D16Civic]

whatever the square root of 93.195 is


^he said there is no air resistance or anything, so it sounds like he should just use the basic equations, i could very well be wrong tho

[ProjectWidow]

whatever the square root of 93.195 is


^he said there is no air resistance or anything, so it sounds like he should just use the basic equations, i could very well be wrong tho
thats right, howd u get that?

[imbosile]

nice goin, hey widow, mind sharing some "+" power, lol.

[soul]

ya i just gave you simple equation it did really imply anything else

Nice work thou

[ProjectWidow]

nice goin, hey widow, mind sharing some "+" power, lol.
both you and D16Civic got a + 1


now only 12 more questions to go, lol

[D16Civic]

that equation v(final)^2=V (initial)^2 + 2a(distance)

ur looking for v(final) so u would take the square root of the other side, which ur v(initial) is zero since its starting at rest and 2a * distance equals 93.195

[ProjectWidow]

that equation v(final)^2=V (initial)^2 + 2a(distance)

ur looking for v(final) so u would take the square root of the other side, which ur v(initial) is zero since its starting at rest and 2a * distance equals 93.195
oh i see, thanks man!

[ProjectWidow]

u guys up for a few more problems? lol

[ironchef]

indeed bring it on.

[D16Civic]

yea, sure

[ProjectWidow]

A 0.50 kg rubber ball has a speed of 2.0 m/s at point A and kinetic energy of 6.5 J at point B.
(a) Determine the ball's kinetic energy at A.
_____J
(b) Determine the ball's speed at B.
_____m/s
(c) Determine the total work done on the ball as it moves from A to B.
_____J

[ironchef]

If I remember correctly the formula is ke(j)=.5mv^2 right? If so just plug and chug basically. a would be 2 j, b would be 5.1 m/s, but not sure about c, i forget that formula unless it was just w2-w1, which would make it 4j.

[ProjectWidow]

If I remember correctly the formula is ke(j)=.5mv^2 right? If so just plug and chug basically. a would be 2 j, b would be 5.1 m/s, but not sure about c, i forget that formula unless it was just w2-w1, which would make it 4j.
both a and c were wrong, but b was right. im not to sure either but you got the formula right. *scratched head*

[Hulud]

oh snap

[D16Civic]

is a.) just 1 J (.5 *.5 * (2)^2)

[Hulud]

E=mC^2????

[ProjectWidow]

is a.) just 1 J (.5 *.5 * (2)^2)
thats what i was thinking. I thought I wrote it down but I guess not. Thanks

[ProjectWidow]

E=mC^2????
oh shit really? Dude thanks man! All that in one step, you are a genius!

[ironchef]

both a and c were wrong, but b was right. im not to sure either but you got the formula right. *scratched head*I see why a was wrong, i forgot to multiple it by the .5, my bad. C i wasn't to sure though, it's been over 2 years since i've had physics lol.

[ProjectWidow]

I see why a was wrong, i forgot to multiple it by the .5, my bad. C i wasn't to sure though, it's been over 2 years since i've had physics lol.
yeh have it at the end of the day and by that time I dont really care. its just dragging on and on. lol

[D16Civic]

^i feel ya man, i had it as my last period too right after lunch. It was so hard to stay awake and pay attention at that point in the day.

[ProjectWidow]

^i feel ya man, i had it as my last period too right after lunch. It was so hard to stay awake and pay attention at that point in the day.
yup...i doze off every once in awhile

[Hulud]

oh shit really? Dude thanks man! All that in one step, you are a genius!
i try i try

[ProjectWidow]

shit I still have like 5 more problems left, anyone?

[ironchef]

Shoot again, but see if theres formulas, i cant remember them for shit lol.

[ProjectWidow]

Shoot again, but see if theres formulas, i cant remember them for shit lol.
A 2.3 kg rock initially at rest loses 403 J of potential energy while falling to the ground. Assume that air resistance is negligible.
(a) Calculate the kinetic energy that the rock gains while falling.
___J
(b) What is the rock's speed just before it strikes the ground?
___m/s

The main formula is PE(before) + KE (before) = PE (after) + KE (after)
where PE = mgh
and KE = 1/2mv^2



and another one that should be easy
A cannonball is fired at 50 m/s at an angle of 30 degrees. How high does it go? (Hint: determine the vertical velocity, and use conservation principles.)
___m
I just cant seem to figure it out. I tried doing trig functions but it doesnt work out

[D16Civic]

i dont remember exactly, but doesnt Potential energy just turn into kinetic energy once it starts moving, therefore a. would be 403 J. Its been a little while, so thats probably wrong, but who knows.

[ProjectWidow]

i dont remember exactly, but doesnt Potential energy just turn into kinetic energy once it starts moving, therefore a. would be 403 J. Its been a little while, so thats probably wrong, but who knows.
oh shit!! It was so easy, it was hard. Thanks bro

I would give you rep points but it says I have to spread some love first

[D16Civic]

is b. 18.72 m/s
PE=KE=403=.5(2.3kg)v^2

[ProjectWidow]

figured out how high the cannon goes. was using cosine function instead of sine

[ironchef]

figured out how high the cannon goes. was using cosine function instead of sineWas it 127?

[ProjectWidow]

is b. 18.72 m/s
PE=KE=403=.5(2.3kg)v^2
you would think, right? But I just checked and thats wrong

[ProjectWidow]

Was it 127?
no, it went 31.887
since you find the sine function which is 50sin30
then you use 1/2w^2=gh (KE=PE)

[ProjectWidow]

is b. 18.72 m/s
PE=KE=403=.5(2.3kg)v^2
woops, you are right man! My bad. i put in 18.27 instead of 18.72.

Thanks guys!!

[ironchef]

Wow my physics skills have gone to crap, and to think i have to take physics sometimes in the next 3 semesters :(.

[ProjectWidow]

Wow my physics skills have gone to crap, and to think i have to take physics sometimes in the next 3 semesters :(.
hey its alright. Look at me! Im in physics and cant seem to get a few easy problems done. It just sucks not being able to pay attention at the end of the day

[ironchef]

hey its alright. Look at me! Im in physics and cant seem to get a few easy problems done. It just sucks not being able to pay attention at the end of the dayYea I hear ya, I was barely keeping my head up in history today, its not even that its so boring, but its just towards the end of the day and im just like let me leave haha.

[ProjectWidow]

Yea I hear ya, I was barely keeping my head up in history today, its not even that its so boring, but its just towards the end of the day and im just like let me leave haha.
exactly the way I am, lol

alright last one for the night
Justin throws a 12.0 g ball straight down from a height of 2.0 m. The ball strikes the floor at a speed of 7.5 m/s. What was the initial speed of the ball? Assume that air resistance is negligible.
____m/s

[ironchef]

exactly the way I am, lol

alright last one for the night
Justin throws a 12.0 g ball straight down from a height of 2.0 m. The ball strikes the floor at a speed of 7.5 m/s. What was the initial speed of the ball? Assume that air resistance is negligible.
____m/sIm going to go with either 9.76 or 0 being that it might be a trick question

[D16Civic]

im saying its 4.12 m/s

[ProjectWidow]

im saying its 4.12 m/s
you are the fuckin man!! Whenever I can give you more rep points, you got em!


thanks guys, you both were a big help!!

[D16Civic]

no problem, glad i could help

[ironchef]

How did you solve that one?

[D16Civic]

i just used the formula v(final)^2=v(initial)^2 + 2*a*distance where you are trying to find v(initial). The mass isnt needed since objects will fall at the same rate no matter what their mass is. So then its just plugging in the numbers.
Square root of [(7.5)^2 - 2(9.81)(2)]

[ironchef]

Whoopsie i think i added the 2*9.8*2 instead of subtracting :headslap:,