1. 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

2. 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

3. 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? v=g t –V= (9.81m/s 2 )(0.64s)= 6.3 m/s

4. Problem We are going to calculate the force required to break the skin of an apple…as 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 v=g t 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 fails…splatt

5. Problem http://www.youtube.com/watch?v=90VyvO hPmA0&p=9A7377D11F047397http://www.youtube.com/watch?v=90VyvO hPmA0&p=9A7377D11F047397 http://www.youtube.com/watch?v=aaim3q mxhk0&p=9A7377D11F047397http://www.youtube.com/watch?v=aaim3q mxhk0&p=9A7377D11F047397 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. v=g t

6. 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 (F=ma) required to break the apple skin.

7. 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?

8. Procedure 1.Mass your raw egg, hard boiled egg, apple, and produce from home using the scales. 2.Convert this value into kg. 3.Carefully drop each object from a height that you are sure will NOT break it. 4.Then, slowly increase your drop height. 5.Your must time the free fall of each object carefully. 6.Record all free fall times and note the time that reflects the fall that broke the outer surface of the object. 7.Use time to calculate final velocity for each object v=g t 8.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 9.Use F=ma to calculate force in Newtons (N) 10.Record all data carefully.

9. Data Object Time (s) Final Velocity (m/s) Time (s) Break Final velocity Raw Egg (s) (m/s) Boiled Egg Apple Misc.

10. Data: Outer Surface Fails ObjectFree fall time (s) Final velocity (m/s) Accelera tion (m/s 2 ) Force (N) Raw egg Boiled Egg Apple Misc.

11. V. Analysis One graph…for 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.

12. 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 lab…don’t say you wouldn’t!