<u>Answer</u>
46,200 J
The energy of given out when a substance is losing heat is given by:
H = mcΔθ
Where m is the mass of the substance,
c is the specific heat capacity of the substance and
Δθ is the temperature change.
H = 0.50 × 22 4200
= 46,200 Joules.
I will assume here that the well is sufficiently short so that the time the sound takes to come from the bottom of the well to our ear is negligible.
Since the pebble moves by uniformly accelerated motion, the distance it covers is given by

where

is the gravitational acceleration

is the time the pebble takes to reach the bottom of the well
Therefore, the depth of the well is

and the correct answer is B.
Answer:
Explanation:
For image formation in objective lens
object distance u = 14 +1 = 15 mm
focal length f = 14 mm .
image distance v = ?
lens formula

Putting the values

v = 210 mm .
B )
magnification = v / u
= 210 / 15
= 14
size of image = 14 x 1.1 mm
= 15.4 mm
= 15 mm approx
C )
For final image to be at infinity , image produced by objective lens must fall at the focal point of eye piece . so objective lens's distance from the image formed by objective must be equal to focal length of eye piece that is 21 mm .
21 mm is the answer .
D )
overall magnification =

D = 25 cm , f_e = focal length of eye piece
= 14 x 250 / 21
= 166.67
= 170 ( in two significant figures )
unless...the wall simulaneiously exerts the same amount of force on you.