Aphysics teacher performing an outdoor demonstration suddenly falls from rest off a high cliff and simultaneously shouts . when she has fallen for 3.0 s , she hears the echo of her shout from the valley floor below. the speed of sound is 340 m/s.

Explanation:

When teacher falls into the cliff then she shout for Help at the same time

so here we know that sound will go down and reflect back up

so here in 3 s distance traveled by the sound

now in the same time the distance that teacher will fall down is given as

now total distance traveled by teacher and sound in 3 s

this total distance must be equal to twice the height of the cliff

false

explanation:

boats, things on boats luggage are way more heavy then water.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)