Question

Could you please help me out on this ?
https://www.dropbox.com/s/ruoy47iufbzvb5y/Screenshot%202013-11-02%2005.04.25.jpg

Answer 1

@Callisto

Answer 2

@e.mccormick

Answer 3

@agent0smith

Answer 4

To find time of max height, use \[\Large v_f = v_i + g t\]

Answer 5

bit what's the g here ?

Answer 6

gravity. -9.8m/s^2

Answer 7

omfg. thanks

Answer 8

lol no prob!

Answer 9

I teach AP physics so this crap is very familiar to me.

Answer 10

Do you need more help...?

Answer 11

teachers say crap???!!!!

Answer 12

Yes, i've also yelled at my classes to shutup, and i use crap frequently "this side of the equation is equal to all that crap over there" "After simplifying all this crap..." etc. It's simple, kids understand it.

Answer 13

they are lucky... my teacher gets mad if i say dang it o.o

Answer 14

yeah i'm not the most strict of teachers haha...

Answer 15

wow

Answer 16

oh sorry I was ark for a while ! Yes ! it seems that b is asking me for the max height

Answer 17

You know the time, now use\[\Large h = \frac{ 1 }{ 2 }g t^2\] for h

Answer 18

I have the solution in front of me but, I don't really understand the process so, it makes no good for me

Answer 19

ok

Answer 20

ok and what I find off of this is the maximum height ?

Answer 21

height FROM the cliff top.

Answer 22

It says "What is the maximum height measured from the edge of the cliff ? "

Answer 23

yes, so ?

Answer 24

Yes that's what the h is.

Answer 25

hm so I solved (b) with this one equation ?

Answer 26

for c it has to be something with time again

Answer 27

aaah !

Answer 28

V = v0 + gt for c right ?

Answer 29

You know the time for it to reach the top.

Now find the time from top to bottom, using this equation again \[\Large h = \frac{ 1 }{ 2 }g t^2\] but this time, plug in h as the TOTAL height from top of flight, to ground. Solve for t.

Answer 30

Then add those times together.

That equation you gave won't work, you don't know it's final velocity

Answer 31

oh by the way, this is the solution to part (b) and it seems that I am not having the same result as the one in the paper, He used a somewhat longer method for it

Answer 32

no no I got it correct, my bad

Answer 33

h=0.5gt^2 will work for the height from the cliff.

Answer 34

That's the solution I have for © https://www.dropbox.com/s/7hulr1lwfgw2i72/Screenshot%202013-11-02%2006.12.54.jpg seems that the solution has 2 roots

Answer 35

You can do it that way. The way i show above makes it easier.

Answer 36

ok but , how can I get 2 roots with the easy way ?

Answer 37

apparently there are 2 possible results right ?

Answer 38

why would you want 2? one is a non-realistic time, a negative time.

h is the total height from top of flight to bottom where it lands in the equation above. Then add the time taken to reach the top

Answer 39

Make the work easier by NOT having to use the quadratic formula - that's why i showed you the way i did.

Answer 40

\[t = \sqrt {2h/g} \]

Answer 41

for c ?

Answer 42

Yep, don't forget to add the time for it to reach the top - the t you have there just gives top to bottom.

Answer 43

1.221 + 12/9.8 =2.445

Answer 44

shouldn't there have been a square root...? and where'd 12 come from?

Answer 45

12/9.8 is the t I found from a

Answer 46

and I calculated the square root to 1.221

Answer 47

1.221 can't be right then. sqrt(2h/9.8) has to be bigger than 1.2. Your max height needs to be AT LEAST 75, since it's 75+whatever height it was above the cliff.

Answer 48

h = 7.3 right ?

Answer 49

how can h be 7.3? h is the height above the cliff, plus 75. h is the height of the object at it's highest point, all the way to the ground.

Answer 50

so 7.3 + 75 = 82.300

Answer 51

That looks better.

Answer 52

I like my result :D

Answer 53

:D

Answer 54

c has to be Vmax

Answer 55

the question is, which t to use for V=v0 + gt

Answer 56

For what, ground impact velocity? Use total time.

Answer 57

i gotta go, if you need help i'll be back later or tomorrow.

Answer 58

ok man, a million thanks for your help , be well !