Design a procedure to test a factor(s) that affects a falling coffee filter and that includes appropriate use of apparatus for the control, collection and analysis of data.

This procedure should include the following sections.

• Defining the Problem and selecting variables:
• Controlling the Variables:
• Developing a method for collecting data:

The above information was given to the student by the instructor.  What follows immediately below is the student’s own work.

Problem:  When an object is released from rest, it initially experiences no drag force. As it falls, its speed increases and so does the force of air resistance acting on it. Eventually, the drag force is as large as the force of gravity and then the net force acting on the object is zero. At this point, the speed becomes constant (acceleration is zero from Newton's 2nd law). We call this speed the terminal speed for the object. This lab will investigate force of air resistance acting on a falling coffee filter. Because of the large surface area and low density of these filters, they reach terminal speed soon after being released. How does the mass of coffee filter affect the time it

takes to become a terminal velocity? 

Hypothesis:  

As the mass of the coffee filters inside the packet increases so will the time. This is due to the gravity of force of the coffee filter as it increases when the mass does. Therefore this causes the coffee filter for a need of more air resistance to make the gravity force and air resistance equal.

When falling, there are two forces acting on an object: the weight and air resistance or –cv2. At terminal velocity, the downward force is equal to the upward force, so mg = –bv or

mg = –cv2, depending on whether the drag force follows the first or second relationship. In either case, since g and b or c are constants, the terminal velocity is affected by the mass of the object.

Variables:

        Independent: Mass of coffee filter

Dependent: Time that takes coffee filter to become  

                  terminal velocity

Control:

• Gravity
• Height
• Person who drops the coffee filter/ starts and stop the motion sensor
• Location
• Condition of the class room
• Same motion sensor

Materials: 

• meter stick
• packet of nine coffee filters
• motion sensor
• laptop
• electronic balance for weighing mass.

Experiment Setup:

        

Procedure:

1. The motion sensor should be connected with the laptop and then placed on the floor and be ready for measuring the velocity.
2. Get the packet of nine coffee filters and weigh it for the mass with the electronic balance and record the in the data table.
3. Place the motion sensor on the ground facing upwards and the packet should be above the motion sensor about 2 meters.
4. Press start on the motion sensor and drop the packet of coffee filters. As it reaches the motion sensor click stop. Record the time the coffee filter took.
5. Repeat steps at least 3 to 5 times to get an accurate value.
6. Remove one coffee filter from the packet leaving it as 8 coffee filters. Weight it again, record the mass and place it above the motion sensor.
7.  Repeat procedure 4 and 5
8. Do the same procedures till the coffee filters inside the packet remains one.
9. After noting down all the results, take the average time for trials for the same weight and then compare the time to see whether time is longer for the coffee filters if the mass is high.
10. Use this data to write a good lab report.

Data table below for guide:

Data table: