They can't hear an echo in small room because in it the sound can't be reflected back. For an echo of a sound to be heard,the minimum distance between the source of sound and the walls of the roomshould be 17.2 m. Obviously,in asmall room echoes cannot beheard.
Option (b) is correct.The index of refraction for the glass is 1.52
Explanation:
velocity of light in vacuum= C= 2.99 x 10⁸m/s
Velocity of light in glass = V= 1.97 x 10⁸m/s
The refractive index is given by n=
n= 2.99 x 10⁸/1.97 x 10⁸m/s
n= 1.52
Thus the refractive index of glass is 1.52
Answer:
It will be A. So since its 2 times more the kinetic energy. But then you have to square it 2^2 = 4
the friction forces are smaller than the forward force