The wavelengths of the sounds produced by two horns are 6 m and 7 m respectively. what beat frequency is heard when the horns are sounded on a day when the velocity of sound is 340 m/s?

Explanation:

Wavelength of sound produced is given as

now we know that the frequency of sound is given as

frequency of the other sound is given as

now the beat frequency is given as the difference of the frequency

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards

option number c is the right answer.