# Pytels Dynamics 12.14: particle moves on helix

Alexanddros81

## Homework Statement

When a particle moves along the helix shown, the componentsof its position vector are
x=Rcosωt , y = Rsinωt , ##z=-\frac h {2π} ωt##

where ω is constant. Show that the velocity and acceleration have constant magnitutes,
and compute their values if R=1.2m, h=0.75m, and ω=4π rad/s

## The Attempt at a Solution

for a start I would like someone to tell me by computing vz = dz/dhxdh/dt
what dh/dt is equal to? Since h = 0.75m = constant, then vz=0 and az = 0
Is my asumption correct?

#### Attachments

• 12_14 Pytel.jpg
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## Answers and Replies

Homework Helper
Gold Member
You would not take a derivative with respect to h : h and R are parameters which someone would choose to describe a specific shape and size of helix. Imagine a tightly wound screw, then you have h (the gap between adjacent helix "threads") small in relation to R. If h is larger then it will be a "shallower" spiral (imagine a drill bit). so h and R are considered constants, in this case.

Alexanddros81
Can you chek my solution?
My results are the same as Pytels

#### Attachments

• Pytel_Dynamics018.jpg
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scottdave