Stimulus

Question

People drop their phones all the time! It’s estimated that 95 million people drop their phones every year. To protect a phone, a cost-effective case that meets certain criteria is needed.

In the following questions, you will design a solution that protects a phone from colliding with the ground and is inexpensive based on Newton’s Third Law.

Question 1

Part A: List all forces acting on each other when we drop a smartphone on the ground.

(1 point)

Answer 1

When a smartphone is dropped, several forces act on it, and they can be described as follows:

1. Weight of the smartphone (Force of gravity): This is the downward force acting on the smartphone due to gravity, calculated as \( F_g = m \cdot g \), where \( m \) is the mass of the smartphone and \( g \) is the acceleration due to gravity (approximately \( 9.81 , \text{m/s}^2 \)).

2. Normal force (when it impacts the ground): This is the upward force exerted by the ground on the smartphone at the moment of impact. It acts in opposition to the weight of the smartphone and is a result of the ground pushing back against the incoming phone.

These forces act on the smartphone and the ground during the drop and impact. The action-reaction pair according to Newton's Third Law can be stated as:

• The smartphone exerts a downward force on the ground (its weight).
• The ground exerts an equal and opposite upward force on the smartphone (the normal force).

Thus, the forces acting on the smartphone when it drops are:

1. Gravitational force (downward)
2. Normal force (upward, during impact)