Calculating Angular Momentum and Precession of a Toy Gyroscope

  • Thread starter Thread starter cuz937100
  • Start date Start date
  • Tags Tags
    Gyroscope
AI Thread Summary
The discussion revolves around calculating the angular momentum and precession of a toy gyroscope, with specific parameters provided for mass, radius, and spinning frequency. Participants have successfully calculated the angular momentum and torque but are struggling with the precession period. The relationship between torque and angular momentum is emphasized, with suggestions to use the equation for angular velocity of precession. A key insight is that the precession period can be derived from the angular frequency, incorporating a factor of 2π. The conversation highlights the importance of applying these physics concepts correctly to solve the problem.
cuz937100
A toy gyroscope consists of a M = 2.5 kg disk with a radius of R = 2 cm mounted at the end of a light axle r = 7 cm long. The gyroscope spins at f = 47 rev/s. It is held horizontal at one end of its axle and precesses about its stand as shown.

a) What is the angular momentum of the disk about its axle?
b) What is the torque about the point of support due to the weight of the gyro?
c) How long does it take the gyroscope to precess once around?
d) If the radius of the disk and the length of the axle were both doubled (R = 4 cm, r = 14 cm), and the rate at which the disk spins were kept the same, how long would it take the disk to precess once?

I have figured out parts a and b (a.0.148,b.1.72), and I thought that part c would just be the inverse of (part b/part a)(Torque/Angular Momentum) due to the fact that angular precesion is just a frequency meaning the inverse would be the period. This did not work and I can not figure out part d without part c. Can someone please help me with this problem? There is a pic of it attached...
 

Attachments

  • gyro.gif
    gyro.gif
    1.8 KB · Views: 736
Last edited by a moderator:
Physics news on Phys.org
cuz937100 said:
A toy gyroscope consists of a M = 2.5 kg disk with a radius of R = 2 cm ...
HOLY CRAP!




cuz937100 said:
... I thought that part c would just be the inverse of ... (Torque/Angular Momentum) due to the fact that angular precesion is just a frequency meaning the inverse would be the period.
It seems to be just an issue of a factor of 2π. τ/L = ANGULAR frequency of precession. Recall:

f = ω/2π

=>

T = 2π/ω

That's my suggestion.
 
Ok, I understand what you're saying, but how do I apply it to the problem. The help for the problem says

C.HELP: Use the answers from parts (a) and (b).
HELP: The precession rate is the torque divided by the component of the angular momentum that is precessing.
 
Anymore suggestions? I really need help with this one, I have an exam over this section this week...
 
Use the equation torque/(Iw). This will give you your angular velocity of precession. Now you need to take 2pi divided by your result to get it in terms of angular frequency. Glad I could help cuz
 
lol, thanks a lot masamune, i already got it though...And I got it before you did ANDREW...
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Minimal rotational kinetic energy for a gyroscope to precess
Replies
33
Views
2K
Gyroscopic effect in quadcopters
Replies
13
Views
3K
I How to quantify gyroscopic precession torque?
Replies
34
Views
3K
Why did I get this angular momentum problem wrong?
Replies
25
Views
11K
Speed of cylinder rolling along a horizontal surface gathering snow (Solved)
Replies
13
Views
2K
Conservation of Energy and Angular Momentum in a Rotating Train-Disk System
Replies
30
Views
3K
I Precession of a gyroscope in freefall
Replies
10
Views
3K
Dynamic reaction versus Coriolis acceleration of the disk
Replies
1
Views
2K
I What does weight actually do in gyroscopic precession?
Replies
7
Views
2K
Angular speed calculation after an inelastic collision
Replies
20
Views
3K

Hot Threads

Recent Insights

Back
Top