PHY 150 Project Two Case Material Evaluation Report

A&L ENGINEERING Case Material Evaluation Report Newton’s Laws of Motion Newton’s First Law of Motion, the Law of Inertia states that an object in motion stays in motion at constant velocity, and an object at rest stays at rest, unless compelled to change its state by the action of an external force. Newton’s Second Law, the Law of Force defines force as a change in momentum (mass times velocity) over time. Newton’s Third Law, the Law of Action and Reaction states that for every force, there exists an equal but opposite force. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A. Newton’s first law applies to our cell phone case durability study throughout the tests. When the phone is held in the tester’s hand, it will remain at rest. When the tester drops the phone, the force of gravity will continue to act upon the phone. Without a hand pushing back, the phone will accelerate until another object, the earth, forces it to become inert once again. Newton’s second law applies to the durability test as well. Until the cell phone case impacts the ground, its velocity will increase. It will impact the ground with force equal to its momentum, the product of its mass and velocity, over the length of time it takes to fall. Newton’s third law also applies to the durability test. When the cell phone impacts the ground, the ground will apply an equal and opposite force upon the cellphone case. Force Diagrams

Specifications: Test Material Total Mass Collision Time Phone Only (No Case) 6.2 oz = 0.18 kg 0.01 s Silicone 7.9 oz = 0.23 kg 0.05 s Hard Plastic 7.3 oz = 0.21 kg 0.03 s Rubber 9.4 oz = 0.27 kg 0.08 s Velocity Calculations Tip : To begin, think about the drop in two phases: The first phase is from the drop to the moment of first contact with the floor. The second phase is the deceleration at impact. The collision time is the time from first contact with the floor to the instant the phone is momentarily at rest. Test Material Pre-impact Velocity Impact Deceleration Phone Only V = 1.5 m 0.01 s = 150 m / s a = 150 m s − 0 m s 0.01 s − 0 s =− 15000.0 m s 2 Silicone V = 1.5 m 0.05 s = 30 m / s a = 30 m s − 0 m s 0.05 s − 0 s =− 600 . 0 m s 2 Hard Plastic V = 1.5 m 0.03 s = 50 m / s a = 50 m s − 0 m s 0.03 s − 0 s =− 1666.7 m s 2 Rubber V = 1.5 m 0.08 s = 18.75 m / s a = 18.75 m s − 0 m s 0.08 s − 0 s =− 234.4 m s 2 Force Calculations Test Material Pre-impact Velocity Impact Force Phone Only 150 m/s 0.18 kg ∗ 15000.0 m s 2 = 2700 N Silicone 30 m/s 0.23 kg ∗ 600.0 m s 2 = 138 N Hard Plastic 50 m/s 0.21 kg ∗ 1666.7 m s 2 = 350.0 N Rubber 18.75 m/s 2 0.27 kg ∗ 234.4 m s 2 = 63.3 N Modeling Motion

References NASA. (2023, August 7). Newton’s laws of Motion . NASA. https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/newtons-laws-of-motion/ #:~:text=Newton’s%20First%20Law%3A%20Inertia&text=This%20tendency%20to %20resist%20changes,will%20maintain%20a%20constant%20velocity.