A sound wave is travelling along a +ve x-direction with a velocity of 300 m/s and has a frequency of 400 Hz . If its amplitude is 2cm, its equation is

A needle of sewing machine moves in path of amplitude 2 cm and has a frequency at 10 Hz. Then what is its acceleration after (1/40) second after it has crossed its mean position ?

Find the wavelength of electromagnetic waves of frequency 4 x 10^9 Hz in free space. Give its two applications.

A steel ball of mass m is initially at rest on a horizontal frictionless surface. It is struck head on by another steel ball of mass 2m travelling with a velocity of 50 cm/s. Calculate the velocities of the two balls after a collision assuming it to be elastic.