Question

The speed of a pendulum is 0.91 C and its time period is 1.8 sec. Then what will be its period in initial frame.
A. 2 s
B. 1.62 s
C. 1.60 s
D. 1.58 s

Answer 1

@Mashy

Answer 2

my goodness are you dealing with special with relativity?

Answer 3

special relativity

Answer 4

No idea :(

Answer 5

@AllTehMaffs

Answer 6

what do u mean no idea?

u just typed 0.91 C.. i hate 0.91Cs
C = speed of light right?

Answer 7

Ops Sorry . I though u r asking Anyways yeah its C

Answer 8

Speed of light

Answer 9

so you are taking course on special relativity?!

Answer 10

yeah

Answer 11

hooray relativistic maths!

Answer 12

not my forte.. !! see you :P

Answer 13

its ok @Mashy

Answer 14

\[\Delta T' = DeltaT / \sqrt{1-v ^{2}/c ^{2}}\]

Answer 15

Am I right @AllTehMaffs ?

Answer 16

In the inertial frame its time will be dilated, so its time should be longer methinks - 2's the only answer that's bigger. We can check though!

\[ \Delta t_{inertial} = \gamma \Delta t_{pendulum}\]

which is your t' and t?

Answer 17

\[ \gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}\]

Answer 18

t' is time dilated and t is time at rest

Answer 19

And time "at rest" is the time in the frame of the pendulum, yah?

Answer 20

yes

Answer 21

then yooz right! although I'm getting the wrong answer with it :/

Answer 22

which one is correct ?

Answer 23

oo.. its that simple? :D.. i thought that equation only worked for relativistic masses :D

Answer 24

time dilation and length contraction, too ^_^ All derived from the same 4-space vector

Answer 25

err, opposite for length contraction

Answer 26

oh i ll be darned!

Answer 27

I still dunno why the answer it's giving isn't right though :/ Are you sure it was .91c?

Answer 28

we have to find period in initial frame . Is it Delta T ?

Answer 29

.74 sec is mine answer ..

Answer 30

I got 4.3 sec....

Answer 31

t = time observed in the other reference frame

t0 = time in observers own frame of reference (rest time)

v = the speed of the moving object

c = the speed of light in a vacuum

Answer 32

yahyah, and the speeds are all given in the frame of the pendulum, right? I mean, even if they weren't, there's no combination of those numbers that gives any of those answers...