Some boffin work required
Some boffin work required
(OP)
Okay this is an unusual one.
We have a casting that i want to see what happens when i impact it. Now my plan isnt complicated (just as well), but i plan to use an steel 'H' beam and drop it from a height. I want to measure simply (no need to include air resistance, wind drift and the like );
a) the velocity at impact
B) Force on impact
Now my caluclations are
Mass m = steel beam = 25kgs
Gravity g = 10 m/s-1
height h = 5 m
therefore Potential energy stored would be
Pe= m.g.h
=1250 Joules
Kenetic Energy at impact is 1/2mv2
and assuming that all Pe = Ke then.
1250 = 1/2(25)v2
= 10ms
this i think is the velocity upon impact. Any idea what that is in real money i.e Miles per hour.
Now the force upon impact i thought would just be
F=MA,
but the more i think about it, it surely depends on the dent it leaves in the casting. or at very least the height that it is dropped from.
I know i ask the strange one, but hey it keeps it intresting
We have a casting that i want to see what happens when i impact it. Now my plan isnt complicated (just as well), but i plan to use an steel 'H' beam and drop it from a height. I want to measure simply (no need to include air resistance, wind drift and the like );
a) the velocity at impact
B) Force on impact
Now my caluclations are
Mass m = steel beam = 25kgs
Gravity g = 10 m/s-1
height h = 5 m
therefore Potential energy stored would be
Pe= m.g.h
=1250 Joules
Kenetic Energy at impact is 1/2mv2
and assuming that all Pe = Ke then.
1250 = 1/2(25)v2
= 10ms
this i think is the velocity upon impact. Any idea what that is in real money i.e Miles per hour.
Now the force upon impact i thought would just be
F=MA,
but the more i think about it, it surely depends on the dent it leaves in the casting. or at very least the height that it is dropped from.
I know i ask the strange one, but hey it keeps it intresting
RE: Some boffin work required
It depends on what the casting is sittng on when it is hit.
We built a drop weight impact tester to test carbide tipped brazed tools. 20# weight in a tube. Held up by a rope. Ruler on the side to measure how far it falls. The tube kept it falling straight.
We were looking a flat impact so we a UHMW replacable botton as the impact object.
Tom
RE: Some boffin work required
F=MA is the right formula but the A you need is the deceleration from 10 m/s to 0. I.E. it depends on the height dropped, the depth of the dents, plus how many milliseconds it took to create the dents. I recall a thread in here somewhere that provides better insight.
RE: Some boffin work required
so i take it then it would be near impossible to calculate impact if you could not accurately determin length of impact.
no matter 22 mph will do fine.
RE: Some boffin work required
RE: Some boffin work required
The problem is not that simple. What you have is a question of impact. In such, the force varies with the time, going from zero at the moment of contact, through a maximum, and finally back to zero. What's termed the "impulse" of the impact is the area under that curve. This is equal to the change in momentum of the falling body.
A conversion mnemonic: The nuber of keys on a piano is 88. 88 feet per second is 60 miles per hour.