Question

Kinematics question: -
Plz help:)
Tank & Gun & Bullet question:)

Answer 1

We don't know the speed of the tank's projectile, but we do know the velocity of the sound.

The distance can be calculated as\[d = v_{sound} t_{sound}\]

Then the speed of the projectile can be calculated as\[v_{shell} = {d \over t_{shell}}\]

Answer 2

Alternatively, we can express the speed of the shell in terms of the speed of sound and the time it takes for the sound and shell to reach the target tank if we note that both travel the same distance. Since\[d = vt\]and the distance is the same\[v_{sound} t_{sound} = t_{shell} v_{shell}\]\[v_{shell} = v_{sound} {t_{sound} \over t_{shell}}\]

Answer 3

in my book answer is given u=850m/s

Answer 4

i m nt getting 850 @eashmore

Answer 5

the answer you wrote is for the velocity of shell?

Answer 6

yeah of course

Answer 7

& s= 510 given in answer

Answer 8

510m.

Answer 9

yeah its 850. I get it. Wait i'll describe how i do it.

Answer 10

Oh. I know where I went wrong. I though the observer was on the tank being shot at, not the tank doing the shooting.

Answer 11

thought* ?

Answer 12

the shot is fired and the light is seen after 0.6 sec. Since, the velocity of light is enormous.. you can neglect the time required by light to take a return trip to eye of observer.
So, basically the point is that the time taken by shot (shell) to reach target is 0.6 sec.
let the velocity of shell be v
therefore
s=v*0.6.......... (1)

Now, the sound is heard after 2.1 sec. so, the time taken by sound to reach observer after the explosion takes place is 2.1-0.6=1.5 sec
so, s=340*1.5
therefore s=510m

Putting this value in (1)
v=850 m/s

Answer 13

i didn't understand the point how did u gt 1.5 sec @ujjwal

Answer 14

Yes, thought. Silly keyboard. :-P

Answer 15

^_^

Answer 16

@maheshmeghwal9 the time taken by shot to reach target is 0.6 sec. And the sound is heard after 2.1 sec.
So, the time taken by sound to reach from the point where the target is to the observer is (2.1-0.6) sec=1.5 sec

Answer 17

so is it light or shell who reaches target in 0.6sec ?

Answer 18

It seems there are many things you didn't understand!
Read my answer again.

Or, start doing the easier problems in your book. That will help you learn the basics.

Answer 19

I have done upto 150 problems in kinematics from basic to higher & this is the last
but I didn't gt this point actually.
k! wait a minute I will read ur reply once again:)

Answer 20

And i have mentioned clearly in my above answer "So, basically the point is that the time taken by shot (shell) to reach target is 0.6 sec."
you should read it properly!

Answer 21

but in ur first line u have written that "the shot is fired and the 'light' is seen after 0.6 sec. "

Answer 22

and when is the light seen? At the instant when the shot reaches the target!

Answer 23

I m getting confused:(
Can u make me understand diagrammatically.

Answer 24

what happens when shot reaches target? It explodes.. boom!!
And at the same instant the light is seen.
So, the shot reaches the target exactly (almost exactly) at the same instant when light is seen, which is 0.6 sec in this question.

Now use your brains! Read and re-read the answers.. If you still don't get it, solve more 150 problems! Or else you will find it difficult to get into IIT.

Answer 25

btw it doesn't depend on solving 150 more questions.
It depends on "A person's common sense to understand everything clearly"
however the question's language was a little bit confusing but i gt it now
when i heard 'Boom' from u lol
So in the end
thanx a lot for gr8 explanation:)

Answer 26

Becoz the main theme was explosion BOOOOOOOOOOOOOOMMMMMMMMMM
lllllllllloooooooooooooooooollllllllllllllllllllll

Answer 27

However I will follow u.
I will solve 150 more^_^