24 Jan '10 22:38>1 edit
if a 100 pound person was jumping up and down, how much force would they be exerting on the ground when they land?
assume a height of 10cm on the jump.
assume a height of 10cm on the jump.
Originally posted by joe shmoHmm, let me re-phrase.
100 lb
Originally posted by uzlessHmm.
Hmm, let me re-phrase.
An 100 pound object is dropped from a height of 10cm. Does the object exert more force on the ground when it hits the ground versus when the object is just resting on the ground?
I may have the terms mixed up but you get the idea....is there an increase? how Much?
Originally posted by uzlessOk yes, there is an increase in Force. The increase is due to the impulse
Hmm, let me re-phrase.
An 100 pound object is dropped from a height of 10cm. Does the object exert more force on the ground when it hits the ground versus when the object is just resting on the ground?
I may have the terms mixed up but you get the idea....is there an increase? how Much?
Originally posted by uzlessDo this experiment:
Hmm, let me re-phrase.
An 100 pound object is dropped from a height of 10cm. Does the object exert more force on the ground when it hits the ground versus when the object is just resting on the ground?
I may have the terms mixed up but you get the idea....is there an increase? how Much?
Originally posted by joe shmoYep
Ok yes, there is an increase in Force. The increase is due to the impulse
J(impulse) = Delta(mv) = Integral(F(t)•dt)
So in order to solve for the maximum force we have to have the relationship F(t).
However we could determine F avg. given the time interval for which the momentum changes.
Originally posted by wolfgang59assume zero give.
Yep
Schoolboy physics tells us that Ft = mv-mu
ie The Impulse = the momentum change.
In practice this depends on the materiels involved, are you landing on concrete or a sprung mattress? The more 'give' on landing the larger t and the smaller F.
Originally posted by uzlessassume zero give.
assume zero give.
image you are sitting in the basement and your one hundred pound sister starts jumping up and down on the floor above you. It makes a hell of a lot more noise than if she is just walking around....yet her weight is still the same. How come?
Originally posted by uzlessIt depends on the precise way in which the object (or person) falls on the ground.
Hmm, let me re-phrase.
An 100 pound object is dropped from a height of 10cm. Does the object exert more force on the ground when it hits the ground versus when the object is just resting on the ground?
I may have the terms mixed up but you get the idea....is there an increase? how Much?
Originally posted by wolfgang59Hmm, Ok wolfgang...so if it takes the kid 1 second to come to a rest then the answer is 100 *sqrt(2) Newtons.
[b]assume zero give.
I believe this is an impossibility.
Lets do a little math and change your measurements into SI units, lets say our jumping guy has a mass of 100kg, and assume g=10.
After his little jump of 10cm (S) what is his velocity (v) on landing?
S=1/2 at^2 ; t=sqrt(2S/a)
v=at
so t = sqrt(0.02)
v = sqrt(2)
his momentum i ...[text shortened]... ht)
You can see that for an instantaneous deceleration the force would have to be infinite.[/b]
Originally posted by uzless100 * 2^(1/2) ~ 140 N
Hmm, Ok wolfgang...so if it takes the kid 1 second to come to a rest then the answer is 100 *sqrt(2) Newtons.
Man, what a thoroughly unsatisfying answer.
I was hoping for a simple 300 pounds or something. Kind of like how if you are in an airplane and the pilot banks hard right you'd feel 2 or 3 G's so you could easily just say that in the turn a 100 pound person would feel like they were 300 pounds in a 3G turn.
Originally posted by uzlessPut a G-meter on your head, and another G-meter on your shoe. Then make a jump from (say) two meters down to a concrete floor. What G-meter do you think measures the largest G?
I was hoping for a simple 300 pounds or something. Kind of like how if you are in an airplane and the pilot banks hard right you'd feel 2 or 3 G's so you could easily just say that in the turn a 100 pound person would feel like they were 300 pounds in a 3G turn.