During the last few years, the growing boom of smartphones has given rise to a considerable number of applications exploiting the functionality of the sensors incorporated in these devices. A sector that has unexpectedly taken advantage of the power of these tools is physics teaching, as reflected in several recent papers.1–10 In effect, the use of smartphones has been proposed in several physics experiments spanning mechanics, electromagnetism, optics, oscillations, and waves, among other subjects. Although mechanical experiments have received considerable attention, most of them are based on the use of the accelerometer.1–8 An aspect that has received less attention is the use of rotation sensors or gyroscopes.9,10 An additional advance in the use of these devices is given by the possibility of obtaining data using the accelerometer and the gyroscope simultaneously. The aim of this paper is to consider the relation between the centripetal acceleration and the angular velocity. Instead of using a formal laboratory setup, in this experiment a smartphone is attached to the floor of a merry-go-round, found in many playgrounds. Several experiments were performed with the roundabout rotating in both directions and with the smart-phone at different distances from the center. The coherence of the measurements is shown.

1.
Patrik
Vogt
,
Jochen
Kuhn
, and
Sebastian
Müller
, “
Experiments using cell phones in physics classroom education: The computer-aided g determination
,”
Phys. Teach.
49
,
383
(
Sept. 2011
).
2.
Patrik
Vogt
and
Jochen
Kuhn
, “
Analyzing free fall with a smart-phone acceleration sensor
,”
Phys. Teach.
50
,
182
(
March 2012
).
3.
Patrik
Vogt
and
Jochen
Kuhn
, “
Analyzing simple pendulum phenomena with a smartphone acceleration sensor
,”
Phys. Teach.
50
,
439
440
(
Oct. 2012
).
4.
Jochen
Kuhn
and
Patrik
Vogt
, “
Analyzing spring pendulum phenomena with a smartphone acceleration sensor
,”
Phys. Teach.
50
,
504
(
Nov. 2012
).
5.
Jefferson W.
Streepey
Using iPads to illustrate the impulsemomentum relationship
,”
Phys. Teach.
52
,
54
(
Jan. 2013
).
6.
Patrik
Vogt
and
Jochen
Kuhn
, “
Analyzing radial acceleration with a smartphone acceleration sensor
,”
Phys. Teach.
52
,
182
(
March 2013
).
7.
Jochen
Kuhn
and
Patrik
Vogt
, “
Smartphones as experimental tools: Different methods to determine the gravitational acceleration in classroom physics by using everyday devices
,”
Eur. J. Phys. Educ.
4
,
16
(
2013
).
8.
Joel
Chevrier
,
Laya
Madani
,
Simon
Ledenmat
, and
Ahmad
Bsiesy
, “
Teaching classical mechanics using smartphones
,”
Phys. Teach.
52
,
376
(
Sept. 2013
).
9.
Asif
Shakur
and
Taylor
Sinatra
, “
Angular momentum
,”
Phys. Teach.
52
,
564
(
Dec. 2013
).
10.
Martin
Monteiro
,
Cecilia
Cabeza
, and
Arturo C.
Martí
, “
Rotational energy in a physical pendulum
,”
Phys. Teach.
52
,
561
(
March 2014
).
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