||Conical pendulum |
||To show that the period of motion of a conical pendulum changes only
noticebly at large angles. |
||1D50 (Central Forces)|
- Ball suspended to a thread.
- Clamping material.
- Large paper circle, diam. = 70cm.
- Small paper circle, diam. = 15cm.
- Stopwatch with large display.
- Small ball suspended to a thread
- Set up the conical pendulum as shown in the Diagram. Place the small
paper circle under the pendulum and make the pendulum swing conically
along the circumference of the paper circle. Measure the time needed for
Repeat this procedure, but now with the large paper
In our set-up, the times measured are 18.2 and 17.5sec
- Take the small simple pendulum by hand and make it swing conically.
Gradually speed it up. At very large angles the increase in the angular
speed is noticed easily.
||Theory tells us that the period (T) of a conical pendulum is
given by (see
Figure1). So |
The table in Figure2 shows
that from 0o to 30o, only changes 7%, while from
60o to 89o this change is about 82%. So only at
large angles T changes noticebly.
- When the pendulum is suspended vertically and not swinging, we have
marked this central position on the table. The paper circles have a hole
in their center so that it is easy to position the paper circles in the
right place (hole and mark coincide).
- Making the pendulum swing along the circumference of the paper
circle needs some practice. Launch the suspended ball tangentially and
give it a speed so that it just reaches a deflection equal to R
of the paper circle (see Figure3).
||Figure 3 |