Pendulums
Supplemental Instruction
Iowa State University / Leader: / Nick S.
Course: / Phys 221
Instructor: / Wetstein
Date: / 3/26/2018

Equations:

Pendulums with massless string of length l and a suspended mass mwith small displacements → ω=√(g/L), ϴ = ϴ0cos(ωt + φ)

Rigid Body Pendulum:

ω = √((mgd)/I)

Torsional Pendulum:

τ = -κϴ

ω = √(κ/I)

ϴ = ϴmcos(ωt + φ)

Body:

1. A simple pendulum has a frequency of 0.5 Hz on the moon (g = 1.6 m/s2). What is the period of the pendulum? What is the length of the pendulum?
1. Tarzan swings on a vine and covers a horizonal distance of 6.2m. Find the minimum length of the vine for SHM to occur.
1. An alien pushes his child on a swing set on Planet YYZ. The super intelligent child becomes upset if he swings outside the range of SMH. Their parent pushes them with a frequency of 0.12 Hz and the swing has a length of 4m, Find the planet’s gravity.
1. A torsion pendulum is made from a disk of mass m = 6.6 kg and radius R = 0.68 m. A force of F = 45.4 N exerted on the edge of the disk rotates the disk 1/4 of a revolution from equilibrium.

1)What is the torsion constant of this pendulum?

2)What is the minimum torque needed to rotate the pendulum a full revolution from equilibrium?

3)What is the angular frequency of oscillation of this torsion pendulum

1. A rod of length 6 L long has a disk with r = L attached to it. The disk can be positioned along the rod’s length. Both the rod and the disk have mass m. The distance between the center of the disk and the pivot point is 3 L in case A and 5 L in case B. Find the ratio of ωa/ωb