What are the reasons for the freefall method being an inaccurate measurement of gravity?

The free fall method is inaccurate for numerous reasons:

1. Air drag is inevitable, such that you can never truly achieve free fall of your object of interest. Modeling air drag is difficult in introductory physics, because it converts your math from algebra to differential equations.

2. Earth's gravity is so strong that the kinematics are fast and hard to measure as humans. Your reaction time can play a significant role when using timing devices.

3. If you use the ticker tape method, it can be inaccurate because part of the ticker tape is moving horizontally, slowing down your result. Also, while ticks occur, they apply friction impulses to the ticker tape.

A more accurate method is Atwood's machine. Atwood's machine allows you to still accelerate objects with gravity being the primary cause of motion, but it allows you to slow down the resulting kinematics and have an easier time timing on your objects. This way, human reaction time is less significant. Also, slower speeds mean less air drag as well, since air drag increases with speed.

Because you aren't in a perfect vacuum, so your object is slowed by air resistance, thus giving you an incorrect result.