Question

A boy steps forward and gives a door a strong push. He contacts the door at time t0, applying a constant force until time t1, causing the door to open. The door slows down due to friction, and stops moving at time t2. Sketch a graph depicting the net force on the door as the door moves.

Answer 1

Analyze the dynamics on each time interval in order to make a graph.

From t₀ to t₁:

During this interval, the boy applies a constant force F.

If the direction in which this force is applied is considered as positive, then the graph will look like a horizontal line on a positive coordinate during this time interval.

From t₁ to t₂:

On this time interval, the friction slows down the door. Friction can be described as a constant force that opposes the motion of objects. Let's represent it using the letter f.

Then, it can be graphed as a horizontal line on a negative coordinate during this fime interval.

Then, the graph should look like the following: