IIT JEE , AIEEE Forum - Physics , Optics

ron_jay

A gun of mass M fires a bullet of mass m with a horizontal speed V. The gun is fitted with a concave mirror of focal length f facing towards the receding bullet. Find the speed of separation of the bullet and the image just after the gun was fired?

Skrishnasharma

when bullet is between focus and pole

speed of sepration is infinity

when bullet is at focus

speed of sepration is infinite

when bullet is between focus and centre of curvature

speed of seration is a quantity not equal to zero and infinity

when bullet is at centre of curvature

speed of sepration is zero

when bullet is behind the centre of curvature

speed of seration is a quantity not equal to zero and infinity

when bullet is at infinite

speed of sepration is infinity

svj29

sorry dude ur answer is wrong...

m1v1 = m2v0

v1 = m2v0/m1

dv/dt = -(v/u)whole square du/dt

(v/u) whole square is = 1 as the object is at pole at the time of firing..

dv/dt = - du/dt

Using vector form: ie light rays are not actually vectors, but on treating them like vectors:

[V= velocity, o =object, m =mirror, i = image.]

-du/dt = - Vom

dv/dt = -Vom = Vme - Voe

dv/dt = v1 - (- v0)

Vim = v1 + v0 = Vie - Vme

therfore: Vie = 2v1 + v0

Vio = Vie - Voe

= 2v1 - v0 - (-v0)

= 2(v1 + v0)

from here you can put the value of v0 in terms of m1 and m2

svj29

hey dude, is mah ansr crct...???

Skrishnasharma

infinite

celestine

Its not infinite
ITS
(f/f-1)^2 *((M+m )/ M)* V

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