Objective: To calculate the force needed to break an apple skin, raw and hard boiled egg shells, and various produce.

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Objective To calculate the force needed to break
an apple skin, raw and hard boiled egg shells,
and various produce.
A Calculation of Force Lab
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Background

• Objects move in both vertical and horizontal
  direction in the shape of a parabola
• This is because the only force acting on the
  object in motion is gravity
• Motion like this behaves in very predictable ways
  with regards to time, velocity and distance

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Background

• Remember our practice problems..
• We can use time to calculate final velocity
• An apple falls from a tree in 0.64s. What was the
  velocity of the apple at impact? vgt
• V (9.81m/s2)(0.64s) 6.3 m/s

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Problem

• We are going to calculate the force required to
  break the skin of an appleas well as other fun
  stuff.
• First we measure time from the top of the
  parabola to the moment it strikes the ground.
  Some things can just be dropped.
• Then we calculate final velocity vgt
• This value becomes the initial velocity in the
  compression part of the fall
• During compression, the object experiences the
  full force of impact as it rapidly decelerates to
  a stop.
• If this force is great enough, then the outer
  shell failssplatt

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Problem

• http//www.youtube.com/watch?v90VyvOhPmA0p9A737
  7D11F047397
• http//www.youtube.com/watch?vaaim3qmxhk0p9A737
  7D11F047397
• Once a falling object comes into contact with the
  ground is compresses.
• If it falls from a high enough distance or lands
  on a hard enough surface the object will break
  apart.

V (initial) Velocity Final 0
Compression At impact
The initial velocity is the final velocity from
the previous calculation. vgt
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Problem

• By using a coefficient for compression
  appropriate for grass (0.15). We can use the
  change in velocity and calculate acceleration of
  compression
• Vf-Vi acceleration of compression
• 0.15
• Finally, we use the mass of the object, the
  acceleration of compression, and calculate the
  Force (Fma) required to break the apple skin.

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Hypothesis

• You have to construct this now. Our analysis will
  contain and discuss numbers, We do not just want
  to guess numbers. So, for now just hypothesize
  the about the method. We will be measure time of
  flight. We will calculate final velocity at
  impact. Can we then use this data to calculate
  the force required to break the outer surface of
  apples, eggs, and produce?

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Procedure

• Mass your raw egg, hard boiled egg, apple, and
  produce from home using the scales.
• Convert this value into kg.
• Carefully drop each object from a height that you
  are sure will NOT break it.
• Then, slowly increase your drop height.
• Your must time the free fall of each object
  carefully.
• Record all free fall times and note the time that
  reflects the fall that broke the outer surface of
  the object.
• Use time to calculate final velocity for each
  object vgt
• Use this final velocity as the initial velocity
  in the acceleration of compression calculation.
  Use 0.15 as coefficient of compression.
  a(compression)Vf-Vi ?
• 0.15
• Use Fma to calculate force in Newtons (N)
• Record all data carefully.

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Data
Object Time (s) Final Velocity (m/s) Time (s) Break Final velocity
Raw Egg (s) (m/s)
Boiled Egg
Apple
Misc.
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Data Outer Surface Fails
Object Free fall time (s) Final velocity (m/s) Acceleration (m/s2) Force (N)
Raw egg
Boiled Egg
Apple
Misc.
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V. Analysis

• One graphfor every time of every object you
  dropped
• Velocities (y-axis) over time (x-axis)
• This is an acceleration graph
• Show units
• Draw line of best fit through the scatter plot.

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VI. Conclusion

• Did you support or reject your hypothesis?
• Which object required the most force to break?
• The least
• What were some sources of error?
• How would you improve this labdont say you
  wouldnt!