Question

photogate timer??

Answer 1

how much times does it take for the first black/clear part to fall through the photo gate timer, starting from the rest

Answer 2

plastic strip has 8 black stripes and 8 clear stripes the width of the black/clear pair is 5 cm

Answer 3

Kinematic equation: X = Xo + VoT + 0.5gT^2

Let your initial position Xo be 0.
Your object starts at rest: Vo = 0.

X = 0.5 * g * T^2 ; where g is gravitational acceleration and T is time

You know g = 9.81 m/s^2
You know the width of a stripe is 5 cm = 0.05 m <-- this is the distance to travel

0.05 = 0.5 * (9.81) * T^2
0.0102 = T^2

T = 0.101 s

This means it takes roughly a tenth of a second for your first black/clear stripe to fall through the photogate.