mph

1
v'25 mph
A
B
40
mph
If the observed horizontal speed of the B?A
volley on board is v'25mph then stationary
observers on the train platform, see it travel
with a speed (1) -25 mph (3) 15 mph (5) 40
mph (2) -15 mph (4) 25 mph (6) 65 mph
2
v'-25 mph
A
B
40
mph
If the horizontal speed of the return (A?B)
volley is v'-25mph then stationary observers on
the train platform see the balls speed as (1)
-25 mph (3) 15 mph (5) 40 mph (2) -15
mph (4) 25 mph (6) 65 mph
3
v'?40 mph
A
B
40
mph
What if v'?40mph?
4
Frame
B
5
v2B3 m/sec
v1B0
m/sec
1 kg
1 kg
A
Frame
5
Within Frame B a mass, m, is accelerated from
rest by a force F through a distance d.
Frame
B
u
a
m
d
A
Frame
6
ConcepTest
In Galilean or Newtonian Relativity, which of the
quantities below change when you change your
reference frame?

• velocity
• distance
• mass
• 4) acceleration
• 5) all of the above
• 6) 1 and 2 only

7
ConcepTest
In Galilean or Newtonian Relativity, which of the
quantities below change when you change your
reference frame?
1) time 2) mass 3) force 4) all of the above 5)
none of these
8
How do you tell when you are completely stopped?
9
The common sense rule you apply is Though
according to spectators on board the train
volleys are simply left-right-left-right-left-righ
t-left the ground-based observers actually see
the ball always traveling left,
but fast-slow-fast-slow-fast-slow-fast
horizontal speed of the B?A volley
(6) 65 mph
horizontal speed of the A?B volley
(3) 15 mph
(6) 1 and 2 only
Sure mass doesnt seem to be something affected
by being in a moving compartment. But if
velocity is, why wouldnt acceleration be? Recall
the definition a?v/?t (vfinal-vinitial)/?t.
Since vAfinal vBfinal Vrel and vAinitial
vBinitial Vrel then ?vA ?vB !
5) none of these
We call such absolute quantities invariant.