This paper describes a conservation of momentum experiment using just smartphones and two beach balls, thus making the experimental study of this movement available to any classroom. For a more thorough analysis of the data, a computer can also be used. Experiments making use of smartphone sensors have been described before, contributing to an improved teaching of classical mechanics. In this experiment, we have made use of two smartphone cameras together with the VidAnalysis free app to track the position of two balls colliding in air during a projectile motion (Fig. 1).

1.
J.
Chevrier
,
L.
Madani
,
S.
Ledenmat
, and
A.
Bsiesy
, “
Teaching classical mechanics using smartphones
,”
Phys. Teach.
51
,
376
(
Sept.
2013
).
2.
J.
Hall
, “
More smartphone acceleration
,”
Phys. Teach.
51
,
6
(
Jan.
2013
).
3.
S.
Mau
,
F.
Insulla
,
E. E.
Pickens
,
Z.
Ding
, and
S. C.
Dudley
, “
Locating a smartphone’s accelerometer
,”
Phys. Teach.
54
,
246
247
(
April
2016
).
4.
M.
Monteiro
,
C.
Stari
,
C.
Cabeza
, and
A. C.
Marti
, “
The Atwood machine revisited using smartphones
,”
Phys. Teach.
53
,
373
374
(
Sept.
2015
).
5.
A.
Shakur
and
J.
Kraft
, “
Measurement of Coriolis acceleration with a smartphone
,”
Phys. Teach.
54
,
288
290
(
May
2016
).
6.
F.
Tornaría
,
M.
Monteiro
, and
A. C.
Marti
, “
Understanding coffee spills using a smartphone
,”
Phys. Teach.
52
,
502
503
(
Nov.
2014
).
7.
P.
Vogt
and
J.
Kuhn
, “
Analyzing simple pendulum phenomena with a smartphone acceleration sensor
,”
Phys. Teach.
50
,
439
(
Oct.
2012
).
8.
P.
Vogt
,
J.
Kuhn
, and
S.
Müller
, “
Experiments using cell phones in physics classroom education: The computer-aided g determination
,”
Phys. Teach.
49
,
383
384
(
Sept.
2011
).
9.
S.
Becker
,
P.
Klein
, and
J.
Kuhn
, “
Video analysis on tablet computers to investigate effects of air resistance
,”
Phys. Teach.
54
,
440
441
(
Oct.
2016
).
10.
S.
Gröber
,
P.
Klein
, and
J.
Kuhn
, “
Video-based problems in introductory mechanics physics courses
,”
Eur. J. Phys.
35
(
5
),
055019
(
2014
).
11.
P.
Klein
,
J.
Kuhn
,
A.
Müller
, and
S.
Gröber
, Multidisciplinary Research on Teaching and Learning, edited by
Wolfgang
Schnotz
,
Alexander
Kauertz
,
Heidrun
Ludwig
,
Andreas
Müller
, and
Johanna
Pretsch
(
Palgrave Macmillan
UK, London
,
2015
), pp.
270
288
.
12.
P.
Klein
,
S.
Gröber
,
J.
Kuhn
, and
A.
Müller
, “
Video analysis of projectile motion using tablet computers as experimental tools
,”
Phys. Educ.
49
(
1
),
37
40
(
2014
).
13.
Tsaedek
,
VidAnalysis free v. 1.63
(Google Play,
2017
), https://play.google.com/store/apps/details?id=com.vidanalysis.free (temporary web address).
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