40mph

v'=25 mph

If the observed horizontal speed of the BA volley on board is v'=25mphthen 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

40mph

v'=25 mph

If the horizontal speed of the return (AB) volley is v'=25mphthen stationary observers on the train platform see the ball’s speed as

(1) -25 mph (3) 15 mph (5) 40 mph(2) -15 mph (4) 25 mph (6) 65 mph

40mph

v'=40 mph

What if v'=40mph?

5m/sec

Frame

Frame

v2B=3 m/sec

1 kg1 kg

v1B=0

u

Frame

Frame

am

d

Within Frame B a mass, m, is accelerated from rest by a force F through a distance d.

ConcepTestConcepTest

In Galilean or Newtonian Relativity, which of the quantities below change when you change your reference frame?

1) velocity

2) distance

3) mass

4) acceleration

5) all of the above

6) 1 and 2 only

ConcepTestConcepTest

1) time

2) mass

3) force

4) all of the above

5) none of these

In Galilean or Newtonian Relativity, which of the quantities below change when you change your reference frame?

How do you tell when you are completely stopped?

horizontal speed of the BA volley

(6) 65 mph

horizontal speed of the AB volley

(3) 15 mph

The common sense rule you apply is

Though according to spectators on board the train volleys are simplyleft-right-left-right-left-right-left…the ground-based observers actuallysee the ball always traveling left, but:fast-slow-fast-slow-fast-slow-fast…

oArelativeBtframeBframeA vvv

(6) 1 and 2 only Sure mass doesn’t seem to be something affected by being in a moving compartment. But if velocity is, why wouldn’t acceleration be?Recall the definition: a=v/t =(vfinal-vinitial)/t. Since vA

final= vBfinal+ Vrel and vA

initial= vBinitial+ Vrel then vA= vB !

5) none of these We call such absolute quantities invariant.