Homework Questions

[ME_student]

Good afternoon everyone,

Here is my homework question:

A hot air balloon is ascending at the rate of 12m/s and is 80m above the ground when a package is dropped over the side. (a) How long does the package take to reach the ground? (b) With what speed does it hit the ground?



Do I set package=-9.8m/s^2 ? A long the y-axis I am going to make up + and down -. V initial balloon=12m/s and we have a height h=80m.


#2 Question

Figure 2-26 which is the excel file, depicts a motion of a particle moving along an x-axis with a constant acceleration. The figure's vertical scaling is set by Xs=6.0m. What are the (a) magnitude and (b) the directions of acceleration?

hm #37.xlsx

I am not 100% sure how to start this problem... I am assuming I need an equation, but I am not exactly sure how to obtain the equation. Can I use one of the kinematic equations to obtain a formula?

Thank you everyone for your help.

[zeke]

Judging from the fundamental questions you are asking, you need a fundamental understanding
of Newton's equations .
You should either crack a book or get a tutor to give you that help immediately, if not sooner.

[wmapettengill]

How to get started...

The balloon AND book are BOTH ascending at 12 m/s until the moment of release, which is 80 meters above the ground. The book will continue upward at a slowing rate: the balloon continues at 12 m/s, while the book decelerates at -9.8 m/s*s.
The book will reach zero velocity at some height GREATER than 80 meters, then accelerate back towards the ground at -9.8 m/s*s.

So, draw yourself a diagram: initial conditions are velocity 12 m/s, accelleration is -9.8 m/s*s. You want to solve for time (t) when the negative acceleration (towards the Earth, caused by gravity) is going to cancel the postive (up) velocity. At this point velocity = 0.
Your equation will like Velocity (value = 0 ) = initial velocity (+ 12 m/s) + acceleration over time (-9.8 meters / seconds squared). It's a fairly simple equation to solve for "seconds squared", then take the square root to find seconds.
This is the time (s) that the book took to come to a stop (in mid air, just for a moment).

Now you can plug that TIME into an equation for height. The height at which it stopped (V = 0) is the initial height (80 m) plus the distance travelled during the time it took to come to a stop. (I'll let you do your homework on that one and find the right equations.)

Good luck

{ edit } Being way too generous with homework questions. Please read our TOS. It is kinda-OK to help in vague terms, but I think that last par gave away the farm.
{ /edit }

[ME_student]

I had asked a tutor to point me in the right directions for the 2nd question. I used ax^2+bx+c=0 and then for the 1st question I figured out. I feel stupid for not figuring it out sooner. (Haha)

[ME_student]

I understand it can be difficult to help me with HW questions without giving me the answer. Thank you.