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The Awesome Egg Drop: Physics Period 9
Transcript of The Awesome Egg Drop: Physics Period 9
mass x ∆velocity
(You can't change the mass as it falls, and the velocity depends on the height it drops from.) What You Can't Change Directly: What You Can Change Directly: Impulse: Force x time
( You CAN change the time it takes
to stop!) - SO: The actual impulse and change in momentum
will be the same no matter how we cushion the egg:
we it will be the same mass slowing to zero velocity.
-BUT: By increasing the TIME (t) the egg takes to change its
momentum, we decrease the FORCE (F) on the egg! Less Time to Stop, More Force= SPLAT.
More Time to Stop, Less Force = Success. So: we needed to increase the TIME on impact our egg took to stop moving. Air Resistance What We Did: Applying the Equations To Put it Bluntly: Remember: FORCE is what breaks the egg - the shell can only stand so much force upon impact. Example:
In this Force-Time Graph,
IMPULSE is the area
under the curve! You can decrease this...
(force) By increasing this!
(Time it takes to change velocity) But Wait! There's More: Applying Impulse to
REAL LIFE Collisions Two Ways to Decrease the Force on the Egg:
(and hopefully prevent it from cracking) The "Right" Way: Make it Take More Time to
Change Velocity on Impact Based on the Impulse-Momentum Theorem
Increase Time on impact to decrease force on egg
Icosahedron with suspended egg in center The Loophole-Finding, Far-More-Effective Way:
Use Air resistance to Manipulate Velocity as It Falls - Structure has lots of "give": the straws collapse, and the elastic strings that suspend the egg stretch, so the egg takes more time to stop
- Instead of hitting concrete and stopping instantly - cushioning the egg using the shock-absorbing and shock-distributing structure means less force on the egg as it stops
- The overall impulse/momentum is the same Why an Icosahedron? - 20 triangles
-Triangles = great shock absorbers!
-Distribute force: when the structure
hits the ground, the icosahedron acts
as very good cushioning - it collapses,
extending the time that the egg takes to
stop (Think: bending your knees when
catching an egg) -Gymnasts: bend knees when landing; martial arts people
learn to "fall correctly" - collapsing their body as they fall
-Same idea of "give": by taking more time to change momentum,
the same impulse can apply less force to the body
(Force breaks bones as well as eggs!)
-Cars: airbags slow the time of a body moving in a crash: use of an object with a lot of give to "cushion" the collision
"Crumple zones" - areas made to "crush" upon impact in the car's frame - also use the momentum-impulse theroem to limit force on passengers
-Helmets: acts as an "air bag" for the head, padding slows the time of the head moving, lessens the force on the head - Use of a "parachute" of sorts: four sheets of newspaper, taped to prevent air from flowing through the parachute
- Large amount of surface area catches as much air as possible to slow decsent
- Made of a fairly lightweight material, very thin so not as to have too much mass, and therefore less overall momentum. Ft=m(Vf-Vi) The parachute changes the VELOCITY of the falling egg:
instead of increasing the TIME to decrease FORCE, it lessens the overall momentum and impulse -Bumper Cars: The huge springs and
rubber bumpers also increase the time it
takes for colliding cars to stop, decreasing the
force on the poor children/oversized adults inside
(Because dying is bad in a ride that revolves around
collisions!) Thanks To....
(References from Helpful Sources) Nave, R. (2006, January). Elastic and Inelastic Collisions. Retrieved May 24, 2011, from Georgia State University website:http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html
Pettis, B. (2007, February 5). Egg Drop Strategies. Retrieved May 20, 2011, from Make: Online website: http://blog.makezine.com/archive/2007/02/egg-drop-strategies.html
Tyler, T. (n.d.). Hex-dome. In Straw and String Models. Retrieved May 22, 2011, from Hex-Dome Structures website: http://hexdome.com/models/straws/index.php
Henderson, T. (2011). The Impulse-Momentum Change Theorem: Real-World Applications. Retrieved May 25, 2011, from The Physics Classroom website: http://www.physicsclassroom.com/class/momentum/ u4l1c.cfm
Drag in aerodynamics. (2011, May). Drag (Physics). Retrieved May 25, 2011, from Wikipedia website: http://en.wikipedia.org/wiki/Drag_(physics) Note: the thickly cushioned landing mats add to the effect! THE END