# Inertial disk lab

1. Oct 29, 2005

### agentd00nut

Ok, in my Physics 11 H class we did a lab with an inertial disk (a disk with a hub in the center, a string is attached to the hub like a huge half a yoyo where the yoyo is stationary and weights are the fingers falling down) and i need to be able to calculate the tension in the string for various weights attatched to the end of the strings. im pretty sure that just using T=ma will work or maybve do something with tension but i dont know where the radius of the hub comes into play and the weight of the disk, any help would be greatly appreciated the diamter of the hub is 76 cm and the disk is 25 cm i calculated the acceleration of a 69.9 gram weight to be .039 m/s^2 and it falls 1.75 meters in a 6.69 second period so using my logic t= .669 * .039 is that correct?

Last edited: Oct 29, 2005
2. Oct 29, 2005

### lightgrav

let's see, if it starts from v=0 and moves 1.75 m in 6.69 s,
its avg velocity is 0.2616 m/s .
the final v = .5312 m/s , same as its change of velocity.
the acceleration is 0.0782 m/s/s . Where's your .039 from?

the mass (0.0669 kg !) is pulled down by gravity, up by Tension.
Most places use g = 9.81 N/kg unless you know yours better.
The SUM of Forces cause the mass to accelerate.