The frequency of the wave is 4 Hz
Answer:
A simple pulley is a wheel with a rope that allows you to pull one end and have it lift whatever is on the other end. A modern, common example of this is a crane, often used in construction.
Explanation:
Switch because look A switch detects the speed that given device can handle and communicates with it at that speed
mass of the box = 20 kg
force of friction on the box due to surface



similarly kinetic friction on it



now the weight of the suspended block will be

so here the weight of the suspended block is less than the limiting friction on it
So here we will say that friction will counter balance the weight of the suspended block and it will not move at all
So acceleration of the box will be zero
Answer:
The path difference between the two waves should be one-half of a wavelength
Explanation:
When two beams of coherent light travel different paths, arriving at point P. If the maximum destructive interference is to occur at point P , then the condition for it is that the path difference of two beams must be odd multiple of half wavelength. Symbolically
path difference = ( 2n+1 ) λ / 2
So path difference may be λ/2 , 3λ/ 2, 5λ/ 2 etc .
Hence right option is
The path difference between the two waves should be one-half of a wavelength.