View Single Post
 
Reply
Posted 2004-02-24, 09:42 PM in reply to Demosthenes's post starting "11. A: Approximately 1.54 seconds 11...."
A) The chand has 24 feet to fall before hitting you.
Since I do not know where the naught key is, I will use @ instead.

X = X@ + V@t + 1/2(a)t^2
X@ = 24
V@ = 0
a = -9.81 m/s^2 = -32.2 ft/s^2

So, when X = 0,
0 = 24 - 1/2 (32.2) (t^2)
t^2 = 48/32.2 = 1.4907
t = sqrt(1.4907) = 1.22 seconds (plus or minus, but since time is only positive...)

1.22 seconds.

B)

V = V@ + at

V@ = 0 So,

V = at

t = 1.22 from A)

V@ = (-32.2) (1.22) = -39.3 feet/second

39.3 feet/second downward

C)

There's a much easier way to do this, but I can't remember the equation... Anyhow...

X = X@ + V@t + 1/2 (a) t^2

X@ = 25 feet
V@ = 0
X = 0

0 = 25 - 1/2 (32.2) t^2

t^2 = 50/32.2 = 1.55

t = sqrt(1.55) = 1.25 seconds

V = V@ + at

V@ = 0

V = (-32.2) (1.25) = -40.25 feet/second

Since speed is a scalar and has no direction, the difference is |-40.25 - -39.3| = .95

0.95 feet/second greater

With all physics, regardless of whether or not the problem was worked correctly, there is a 20% chance that those answers are incorrect. If I cared more, I would check the answers, but... I don't care. I only do this because I enjoy it. *sigh*

Btw, this is physics, not math.
D3V said:
This message is hidden because D3V is on your ignore list.
What is it they say about silence being golden?

Last edited by Medieval Bob; 2004-02-24 at 09:45 PM.
Old
Profile PM WWW Search
Medieval Bob enjoys the static noises of ten television sets simultaneously tuned to 412.84 MHzMedieval Bob enjoys the static noises of ten television sets simultaneously tuned to 412.84 MHz
 
 
Medieval Bob