Expert: Daniel Mazur - 3/22/2006

Question
i know algebra and this is double honors physics.i dont need atmosperic influences.ive done the experiment of dropping the egg in the container.I didnt measure time or anything else because it wasnt part of the procedure.-I did this lab where i had to have this ball bounce and i had to find similar stuff buti dont remember how i got it.----------------------mass of ball:.040kg
dropped height(m)=1
Rebound height(m)Avg of 3 trials=.4m
Vbefore=-4.43m/s
Vafter =2.8m/s
Pbefor(kgms)=-.1772
Pafter=.112
Changein Momentum from before bounce to after bounce (kgm/s)=2.98
Impulse applied to ball during bounce(N-s)-2.98
Intervl Of time ball is in contact with floor (sec).008
Average net Froce Applied to ball during bounce9N)=36.13
The mass the interval of timethe dropped height was given the rest we had to figure out.I think the answers i need are similar to this. Change of momentum = to net force times delta time and change of momntum =mass (vf-Vi). If you could just give me numbers that made sense it would help me alot. just straight forward ansers without atmospheric influences.i dropped the eggin the container in free fall. just send me some numbers thank you
Followup To
Question -
i made a container out of sponge that weighs 52 grams. This container was built to save an egg that weighs 54.5 grams being dropped by a height of 4.5 meters.how do i figure out theoretical time it  should take to reach the ground.how do i figure out the velocity of egg+the container during impact?how do i calcculate the momentum of egg+containerjust before impact how do i figure out impulse applied to egg+container when it hits the ground and comes to a stop?
asuming time duration of impact is .005seconds how do i figure out the average net force acting on my egg +container during impact?HELP ME!what physics cocepts in impulse change of momentum could i use to explain results?
Answer -
Hi David,
I need you to tell me more about your task to give you the correct answers.
1) What level of physics and mathematics do you know?
2) Do you want predictions including all atmospheric influences?
3) Are you going to do the experiment in reality? Do you have the tools to measure the real time of flight, time of impact, the maximum deformation of the sponge?
Sorry, this is a problem, where there are seeral answers depending, who's asking and what they need the answer for.
Hope to hear from you.
Take care!
Daniel

Answer
Thanks,
here are some answers and some notes:
1) time t from height h0 to ground:
         t = Sqrt[2h0/g]
2) momentum of egg (mass me) and container (mass mc) just before impact:
        pi = (me+mc)Sqrt[2h0g]
3) impulse (change in momentum from touch to stop):
         I = -(me+mc)Sqrt[2h0g]
4) Average force on egg during impact taking Deltat time: Suppose you know initial h0 height and rebound height h1, then the impulse is
    Deltap = me{Sqrt[2h1g]-Sqrt[2h0g]}
Mind you, this is naturally a NEGATIVE value. Then the average force is
      Favg = Deltap/Deltat
Note: This quantity is not really THE important value to consider, if the egg breaks or not, but is the best we can do without knowing the sponge deformation during impact.
5) Velocity during impact: You have no choice but use the average force, which is not much of a realistic model. However, the question is about time dependence of the velocity, so
      v(t) = vi - tFavg/me, as long as v(t) >= vf (which should be the same as time t <= Deltat)
Remember that vi = Sqrt[2h0g] and vf = -Sqrt[2h1g] (NEGATIVE). Here the time zero is set at the instant of the first touch between the container and ground.

All these results come from simple mass point mechanics in a uniform gravitational field. In addition, conservation of energy helped, although that one is not an independent concept.

I hope these answers help, I am leaving the numerical part to you.
Daniel