When we travel in a train moving at a certain velocity, we observe the stationary objects outside are moving backwards. These stationary objects seem to move due to a relative velocity. Consider that the stationary object outside the train is a man standing on the stationary floor watching a woman moving on a train. The woman on a train will see the man moving backward with similar velocity as her. In kinematics, this magnitude of relative velocity will always be the same whether the man is far away from or near the train, as long as he stands on the stationary floor.

1.
R. A.
Serway
and
J. W.
Jewett
,
Physics for Scientists and Engineers (with PhysicsNOW and InfoTrac)
, 6th ed. (
Brooks Cole
,
2003
)
2.
J.
Walker
,
D.
Halliday
, and
R.
Resnick
,
Fundamentals of Physics
(
Wiley
,
Hoboken, NJ
,
2011
).
3.
Luis
Tuset-Sanchis
,
Juan
C.
Castro-Palacio
,
José
A
Gómez-Tejedor
,
Francisco J.
Manjón
, and
Juan A.
Monsoriu
, “
The study of two-dimensional oscillations using a smartphone acceleration sensor: Example of Lissajous curves
,”
Phys. Educ.
50
,
5
(
2015
).
4.
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
).
5.
Jochen
Kuhn
, “
Relevant information about using a mobile phone acceleration sensor in physics experiments
,”
Am. J. Phys.
82
,
2
(
Jan.
2014
).
6.
Elizabeth
Azhikannickal
, “
Sports, smartphones, and simulation as an engaging method to teach projectile motion incorporating air resistance
,”
Phys. Teach.
57
,
308
(
May
2019
).
7.
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
).
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.