A bird in air is diving vertically over a tank with speed 5 cm/s. Base of tank is silvered. A fish in the tank is rising upward along the same line with speed 2 cm/s. Water level is falling at rate of 2 cm/s.
Answers
Explanation:
8↑w.r.tfish=8-4=4↑(A) speed of fish seen from air
v
fish
air
=v
fish
/μ
water
v
fish
air
=4/
3
4
v
fish
air
=3 upwards
=4×34=3↑
speed of fish w.r.t bird
v
fish
bird
=v
fishair
+v
bird
v
fish
bird
=3+6
v
fish
bird
=9 upwards
8↑w.r.tfish=8-4=4↑(B) Speed of the image of fish formed after reflection from the mirror w.r.t air
v
fish
air
=v
fish
/μ
water
v
fish
air
=4/
3
4
v
fish
air
=3
speed of fish w.r.t bird
v
fish
bird
=−v
fishair
+v
bird
v
fish
bird
=−3+6
v
fish
bird
=3
8↑w.r.tfish=8-4=4↑(C) speed of bird seen from water
v
bird
water
=v
bird
.μ
water
v
bird
water
=6.
3
4
v
bird
water
=8 downwards
=4×34=3↑
speed of bird seen w.r.t fish
v
bird
fish
=v
birdwater
+v
fish
v
bird
fish
=8+4
v
bird
fish
=12 downwards
8↑w.r.tfish=8-4=4↑(D) Speed of image of bird w.r.t water looking downward in the mirror
v
bird
water
=v
bird
.μ
water
v
bird
water
=6.
3
4
v
bird
water
=8
=4×34=3↑
w.r.t fish
v
bird
fish
=v
birdwater
−v
fish
v
bird
fish
=8−4
v
bird
fish
=4