Question

anyone good at kinematic equations from physics?

Answer 1

a football is kicked and it takes 4.4s to hit the ground. What is the maximum height the ball reaches? assume the ball starts at ground level

Answer 2

distance = velocity times time

Answer 3

integrating to get acceleration gives 1/2at^2 where a is acceleration and t is time

Answer 4

the acceleration due to gravity is 9.81 m/s^2

Answer 5

so the distance = (1/2)(9.81)(4.4)^2 = 94.960 m

Answer 6

I was never told you could intergrate to get acceleration from that function!!!!??????? I just doulble checked my notes and it doesn't say that. Plus their answer was ymax=24m

Answer 7

lol wel i have clearly gone wrong. what formula did they use?

Answer 8

yeah ive done this stupidly

Answer 9

so you dont know the initial velocity?

Answer 10

no wait, of course you dont need it

Answer 11

you want y when t = 2.2 with a = 9.81

Answer 12

no all I know is four kinematic equations and the fact that the acceleration is-9.8 (m/s^2) and that the final velocity would equal zero, aside from time equaling zero

Answer 13

i feel like ivanmlerner is going to show us the way

Answer 14

@JamesWolf when I used the equations I know I came up with the same answer you did I don't know how or why. But it is wrong. I wonder how did you come up with 2.2=t?

Answer 15

wel ball reaches maximum height halfway through the time?

Answer 16

is that always true?

Answer 17

it needs to be at its maximum height at 2.2s, then, since h(t)=(1/2)*gt^2, just put t = 2.2, you were in the right way @JamesWolf

Answer 18

i think...

Answer 19

im not sure if its always true, damn i was so close!

Answer 20

hahaha im wrong too

Answer 21

no, that gives 23.74 = 24

Answer 22

oh wait auhuha its right

Answer 23

:)

Answer 24

Of course, because it needs to fall from rest at the max point, during 2.2 sec at aceleration g, no initial velocity and no y0

Answer 25

I just put the origin at the max point.

Answer 26

presuming its terminal velocity is infinate

Answer 27

What do you mean? sorry not native speaker.

Answer 28

no thats fine. i mean the highest point will only be halfway through its flight, if the velocity up is the same as the velocity down

Answer 29

if the velocity down is less, because say it gets slowed by air resistance. then the highest point will be earlier in time

Answer 30

I understand the concept But I am asked to show this using the kinematic equations, which I can't. give me a minute and I will show you all the eqations I am supposed to use

Answer 31

okay

Answer 32

\[x=\Delta t\]