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Your supervisors at A&L Engineering have tasked you with evaluating the durability of three common materials used in the design of cell phone cases. For each material type, you have been asked to determine the force of impact of a phone dropped from a set height above the ground. Using the mass of each case and the collision time, determine the force of impact on each case material and determine which case material offers the most protection.

To facilitate your analysis, you have been provided with specifications for case materials in the table below. However, you may also use your own figures for the mass of phones and test case materials. If you do use a different figure, be sure to make that clear in your analysis. As you use this data, ensure that you have made the necessary SI unit conversions:

Test MaterialMassCollision TimePhone Only (No Case)6.2 oz.0.01 secondsSilicone1.7 oz.0.05 secondsHard Plastic1.1 oz.0.03 secondsRubber3.2 oz.0.08 seconds

Directions

To complete your evaluation of various materials for cell phone cases, you must create a case material evaluation report that describes the motion and impact forces of several phone case materials under evaluation.

Once you have described the relevant laws of motion, create force diagrams to model the motion for a phone dropped from a set height. You should include diagrams, with their respective force vectors, for each phone drop. In your diagrams, address the following:

Define the height you will be using for each phone drop. As the researcher, you will choose a drop height of between 1 and 2 meters.

Using the provided mass of 6.2 oz, or by measuring the mass of a personal cell phone, determine the mass you will be using for your calculations. Remember to add the mass of the case material.

In your diagram, show the direction and name of each force on the cell phone both at the drop point and at the point of collision with the ground.

Following the creation of the force diagram, use the information provided in your case specification document to calculate the velocity before impact and deceleration at impact. Remember that deceleration is represented as negative acceleration in force equations. In your calculations, assume a standard free-fall acceleration during the fall, and a velocity of 0 m/s after the impact. You should include calculations for the following scenarios:

A phone without a case

A phone with a silicone case

A phone with a hard plastic case

A phone with a rubber case

Using Newton’s second law, calculate the force of impact for each scenario.

After you have completed your calculations, describe how force equations model the given scenario. In your description, address the following elements:

Velocity before impact

Acceleration

Force

Finally, using data from your analysis, recommend the best material for a cell phone case. In your recommendations, address the following elements:

Which of the trials results in the lowest force of impact on the phone?

What considerations, in physics or otherwise, might you have in recommending a material for a cell phone case?

Answer 1