Question

How long does it take an acorn to hit the ground after dropping from the branch of a tree 12.5 m high? Remember that g=9.8 m/s^2!

1.0 s, 5.0 s, 2.6 s, or 1.6 s

**not sure about this!! :(

Answer 1

what variables do you know

Answer 2

ie what is given to you

Answer 3

distance=12.5 m ?

Answer 4

so d = 12.5

Answer 5

what else

Answer 6

initial velocity would be 0?

Answer 7

yes, vi = 0

Answer 8

acceleration=9.8 m/s^2 ?

Answer 9

yes a = 9.8

Answer 10

not sure if there's anything else though!

Answer 11

look along the top row of the chart

http://www.studyphysics.ca/newnotes/20/unit01_kinematicsdynamics/chp04_acceleration/images/formulas.GIF

Answer 12

is final velocity known? :/

Answer 13

what letters or symbols do they have

Answer 14

we have a, d, vi

but missing vf and t?

Answer 15

what variable do we want to solve for

Answer 16

t?

Answer 17

we don't need vf, so look for an X under vf and you'll find your formula

Answer 18

okie! so d=vi(t)+1/2(at^2)

12.5=0(t)+1/2(9.8t^2)
=12.5=4.9*t^2/2

? not sure if i did that last part right? :/

Answer 19

you should have 12.5 = 4.9t^2

Answer 20

okie!

ohh okay:)

so divide 4.9 right?
and you get 2.55102040816=t^2 ?

Answer 21

then take the square root of both sides

Answer 22

so the answer will be about t=1.6 s ?

Answer 23

t >= 0

Answer 24

t = 1.59719 or yeah, roughly t = 1.6 seconds

Answer 25

ahh yay!

thank you!!!

Answer 26

np