# Homework Help: Whats going on here?

1. Sep 22, 2009

### intriqet

I have two problems. I have filled in most of the information that is asked but I can't seem to figure out a part for each problem. Please Help.

Problem 1:

1. The problem statement, all variables and given/known data

At a NASA research center free-fall research is performed by dropping experiment packages from the top of an evacuated shaft 146 m high. Free-fall imitates the so called microgravity environment of a satellite in orbit.
a) what is the max time interval for free fall if an experiment package were to fall the entire 146 m?

5.45 s [correct]

b) Actual NASA specs allow for a 5.24 s drop interval. How far do the packages in 5.24 s?

135m [correct]

c) What is their speed at 5.24 s?

51.5 m/s [correct]

d) What constant acceleration would be required to stop an experiment package in the distance remaining in the that shaft after its 5.24 fall?

121 m/s^2 [incorrect]

2. Relevant equations

Kinematic equations

3. The attempt at a solution

Presumably, since the shaft is 146 m tall and the package has already fallen 135 m there are 11 m left for the package to stop.

deltaX = 11 m : Vi = 51.5 m/s : Vf = 0 m/s

this information should be enough to calculate Ax for the second part of the problem but Webassign says my answer is wrong. Any ideas guys?

Problem 2

1. The problem statement, all variables and given/known data

An inquisitive physics student and mountain climber climbs a 48.0 m cliff that overhangs a calm pool of water. He throws two stones verticall downwar, 1.00 s apart and observes that they cause a single splash. The first stone has an initial speed of 1.92 m/s downward. Assume the downward direction is positive.

(a) How long after release of the first stone do the two stones hit the water?

2.93 s [correct]

(b) What initial velocity must the second stone have if they are to hit simultaneously?

16.1 m/s [incorrect]

(c) What is the speed of each stone at the instant the two hit the water?

first stone

30.7 m/s [correct]

second stone

34.62 m/s [correct]

2. Relevant equations

Kinematic equations

3. The attempt at a solution

This seems like a pretty straightforward problem but I can't seem to get question B right even though I used the value for question B to get the correct answer for question D.

2. Sep 23, 2009

### rl.bhat

b)The package is accelerating down wards with g. Your answer is true if the package is moving with uniform velocity. So net acceleration should be ..........?

3. Sep 23, 2009

### intriqet

131 m/s^2 in the upward direction to compensate for g, which is incorrect according to Webassign