Physics!?!?

Question

Ok i noe what ur gonna say. That i sould do my own homework and stop asking but i have tried these 2 question like a million times and i cannot figure them out.
Please help

1) Assuming no air resistance, how long does it take a penny to fall if it was thrown down with an initial velocity of 5.0m/s from the CN Tower (553m)?

2) Superwoman is hovering above the ground when a person free-falling goes by her at a terminal velocity of 39 m/s. Unfortunately, the parachute doesn not open. Fortunately, Superwoman is around. If it takes her 1.9s to realize the person is in distress, what must her acceleration be if she is to catch the parachutist just before she hits the ground 1000m below.?

Please help
U dont have to jus tell me the answers... even if u jus help me understand them it would be much appreciated. If u do show me how to get the answer.. Please show the steps and explain. Thank You in Advance.

Answer 1

1. 553m/5ms = 110.6s or 1min 50.6seconds
2 42.12m/s

Answer 2

(1)
Apply S = ut + ½ at² for downward motion, where s = distance, u = initial velocity, a = acceleration (assume 10ms-2), t = time

Then:
553 = 5.t + ½ (10).t²
t = 10.028 s

(b)Time taken for the (unfortunate) parachutist to hit the ground from the moment he passes S.woman
= 1000m/39 = 25.64 s

SW has only got (25.64 - 1.9) = 23.74 seconds to respond, i.e.: to reach the ground the same time as the parachutist hits ground. And she also has 1000m to travel.
S = ut + ½ at² (Downward motion)
1000 = (0).t + ½ (a).(23.74)²
a = 3.54869 ms-2
Superwoman needs to accelerate at a rate of 3.54869 ms-2, which, given the strengths of the Superwoman, is easily achievable. It's a good thing she does not have to read a map as she only needs to go straight down. Fingers crossed.

Answer 3

s = Vo*t + (1/2) gt² then
553 = 5t + 4.9t²
This is a simple quadratic in t. If you honestly can't solve it, you don't have a prayer in that Physics class.

And the 2'nd problem is very similar.

Doug

Answer 4

ok. ill do number 1.

X- 0 m
Xo- 553 m
V- ?
Vo- (-5 m/s)
A- (-9.8 m/s/s)
T- ?

solving for T

use V^2 = Vo^2 + 2A(X- Xo) to solve for V.

Then use V = Vo + AT to solve for T.

You should get close to -100 m/s for the velocity and then about 10 seconds for the time.

sorry i dont have a calculator with me.

let me know if i helped.

PS- THE TOP ANSWER IS COMPLETELY WRONG. idk about the second one.