TRACK 9. A world of digital competences: mobile apps, e-citizenship and computacional systems as learning tools Authors: Manuela Ramos Silva, Pablo Martin-Ramos and Pedro S. Pereira Da Silva https://youtu.be/BU-ldr-dGzo

1. Testing Physics Laws
with Smartphones
TEEM’16 - Track 9
November 4, 2016 ·Salamanca

2. Authors
MANUELA RAMOS SILVA
PEDRO S. PEREIRA DA SILVA
CFisUC, Universidade de Coimbra
manuela@pollux.fis.uc.pt
psidonio@pollux.fis.uc.pt
PABLO MARTÍN-RAMOS
EPSH, Universidad de Zaragoza
pmr@unizar.es
Presentation template by
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3. Introduction
Why should we incorporate smartphones into our classes?
1

4. “
“This ain't no questions that indeed as
much as I love my laptop that is not the
way world is going to learn. They are
going to learn on tablets and phones.
Better be on board or miss the train.”
Jay Cross (1944-2015)

5. Context
◇Why is the teaching of Physics, Chemistry,
Biology or Geology in high-school so theoretical?
◇Why it is so difficult to do lab classes during the
school year?
The answer is complex, but the main cause is usually
the lack of resources. The classroom has to be split at
least into two groups, which demands more teachers
and space, and an experiment requires equipment,
labware, reagents and such, which are expensive to
buy and difficult to repair…

6. Is there a way out?
Most teenagers own a smartphone and bring it with
them into the classroom, where we either gather then
all before the class or repeatedly announce that they
must be switched off during the entire class…
◇But smartphones are an excellent technological
platform that may give a helping hand when
performing experiments, reducing their cost to
almost zero…
◇They should be incorporated in the classes instead
of banned from them!

7. An example…
An experiment to study projectile motion
and the determination of the acceleration
of gravity.
All we need is a smartphone with a free
burst camera app and a common beach
ball. To analyze the results we need a
computer with a photo editor (or a printer
and a ruler).

8. Is it that simple?
Yes! We are showing results attained in a 1st attempt,
without adjusting the focus of the camera, repeating
the takes or re-measuring the position of the ball.
◇The measurements involved in this experiment
take less than 5 minutes.
◇The study of projectile motion is part of the high-
school curriculum all over the world.
◇Maths involved are simple enough and two types
of movement can be studied, exemplifying the
main Laws of Mechanics: the Law of Inertia and
the Fundamental Law of Dynamics.

9. Goal
That students deal with new
technologies (smartphones
and computers), learn
Physics and enhance their
logic skills

10. Methodology
Equipment needed and how to conduct the experiment
2

11. Equipment used
◇An Android (v5.1.1, Lollipop) smartphone (we
used a Moto G 3rd gen).
◇Fast Burst Camera Lite app (Google Play): “no
delay option” in the app settings so that the
phone would take a photo every 50 ms. approx.
◇Computer with GNU Image Manipulation
Program (GIMP)
◇OpenOffice

12. Results
Photo editing, converting time & position, and plotting & fitting
3

13. Some pictures of the flight of the ball

14. Launch 1: nearly vertical drop
Two experiments
Launch 2: nearly horizontal toss

15. Plot & fit in Calc
Launch 1
The free fall of the beach ball is an
accelerated motion. The Law of Motion
has the form:
𝑦𝑦 = 𝑦𝑦0
+ 𝑣𝑣0
· 𝑡𝑡 + 1/2 · 𝑔𝑔 · 𝑡𝑡
2
Fitting with a 2nd order polynomial:
𝑦𝑦 = 4.97 · 𝑡𝑡2 − 0.35 · 𝑡𝑡 − 0.008
The calculated value of the acceleration
of gravity is 9.94 m/s2.
Launch 1
0
1
1
2
2
3
0 0,2 0,4 0,6 0,8
t (s)
y(m)
If a laptop is not available, the printed photos (all in the
same scale) can also be analyzed using a common ruler.

16. Launch 2: The ball has two distinct and independent
movements in the horizontal and vertical directions.
◇ Horizontally, the ball has a uniform motion with
constant speed: 𝑥𝑥 = 𝑣𝑣0𝑥𝑥 · 𝑡𝑡 = 2.82 · 𝑡𝑡 (Law of Inertia)
◇ On the vertical axis, the movement is uniformly
accelerated with the acceleration of gravity pointing
downwards in the positive direction of the y axis. The
best fit corresponds to the quadratic expression 𝑦𝑦 =
4.87 · 𝑡𝑡2
− 2.07 · 𝑡𝑡 + 0.19, so the experimental
acceleration value is 9.74 m/s2.
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0,01,02,03,0
x (m)
y(m)
Launch 2, Horizontal Axis
0,00
1,00
2,00
3,00
0 0,2 0,4 0,6 0,8 1
t(s)
x(m)
Launch 2, Vertical Axis
0
1
2
3
0,0 0,5 1,0
t(s)
y(m)

17. Conclusions
Outcomes and alternative procedures
4

18. Conclusions
◇The values for the acceleration of gravity
calculated from the two independent launches
were 9.94 and 9.74 m/s2, with less than 2%
difference from the known value of 9.8 m/s2.
◇For a more advanced classroom, there are more
aspects that can be explored with similar data
collections, such as the small difference in ball
acceleration in the upwards and downwards
movement, caused by air resistance.
◇It is also possible to experimentally calculate the
initial ball velocity and compare between
students strengths.

19. Thanks!
Any questions?
You can find me at:
◇ pmr@unizar.es