Newton’s Laws of Motion
The three laws of motion, and their application to the test case are as follows:
- A body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force. The phone will fall under the force of gravity.
- The acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system, and inversely proportional to its mass. Heavier cases will require more force to accelerate and decelerate.
- Whenever one body exerts a force on a second body, the first body experiences a force that is equal in magnitude and opposite in direction to the force that it exerts. When the phone impacts the ground, it will exert its force on the ground, but the ground will exert equal force on it, decelerating it.
Force Analysis
For this report, the forces experienced by the phone falling from a height of 1.88m are calculated. As the drop height and acceleration due to gravity are constant, this speed is 6.07m/s regardless of the phone’s case. However, the force acting on the phone differs depending on its weight:
As the phone falls on the ground, it undergoes deceleration depending on the case, while still experiencing downward acceleration due to gravity. For the phone without a case, this is F = 0.175767kg * (9.8m/s2 – 607m/s2) = 104.913N. The reaction force from the ground is, thus, 104.913 + 1.72 = 106.663N.
Report
Using a rubber case results in the least amount of force on the phone. However, the amount of force is not the only factor to consider when choosing a material for the case. Other physical attributes, such as the material’s ability to resist impact forces. As a phone is a small device one carries most of the time, usually in a pocket or a handbag, the weight and size of the case are also important. Finally, the manufacturing cost of a case is another important consideration. Thus, based on the information provided for the test, the proportion between case’s mass and the impact force it experiences can be used to determine its value. Based on this data, silicone offers a reasonable combination of weight, force of impact, and weight to force ratio.