Work and energy

Consider two observers moving with respect to each other at a speed v along a straight line. They observe block of mass m moving at a distance l on a rough surface. which of the following quantities will be same as observed by the two observers.
a} K.E. of the block at time t
b}W.D. by the the friction
c}Total W.D. on the block
D}acc. of the block.

8 Answers

1
voldy ·

acceleration of the block no?

1
greatvishal swami ·

@ srinath how can the acc be same its a vector quantity & for both of them block is moving in opp direction

i thnk KE & WD(b,c) shud be(???????)
bt i really want sm1 to interfere its an imp Q

11
Anirudh Narayanan ·

I think u're right Srinathl. Better go, wake Barinder up and ask him the answer. He seems 2 hv disappeared
@ Vishal, It doesn't say they are moving in opposite directions. So relative acc for each observer w.r.t the block is 0, isn't it?

1
greatvishal swami ·

bt ani it doesnt even say dat they r moving in same dir

& also they cant move wth same rel velo in same dir (can they try to see my point plzz Q is now confusing me)

ALSO wat bout (a,b,c) they seems rite too

1
voldy ·

I didn't give so much of a thought . saw that they were moving with same velocityies . no acclereation , so going with the general approach that frames with unifrom vel are inertial I wrote it. mine may be wrong. I'm not good in mechanics.

1
greatvishal swami ·

me too srinath bt u better giv last few weeks to dat i got bad rank in iit only due to this factor

1
voldy ·

k . thanks da. I'll do my best.

1357
Manish Shankar ·

acceleration of the block will be same as observed by them as they are moving with constant velocity with respect to each other.

velocity of the block observed by them is different so KE will be different

Also displacement of the block observed by them is different, so work done by friction will be different

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