I'm going to make an assumption here. The speed of the wave is 343m/s = c.
The equation for speed of a wave is c = λf. λ: wavelength f: frequency
Substituting known values, we get 343m/s = λ(784Hz)
λ = 0.4375m
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Answer:
d= 852.01 m
Explanation:
Given that
Speed of sound in air u= 343 m/s
Speed of sound in concrete v= 3000 m/s
Lets take time taken by sound in the concrete is t then the time taken by sound in air will be t+2.2 s .
The distance (d)travel will be same in both the cases.
We know that
Distance = Velocity x time
So
d= 3000 x t = 343 x (t+2.2)
3000 t = 343 t + 343 x 2.2
t= 0.284 s
So the distance d
d= 3000 x 0.284 m
d= 852.01 m
Answer:
a) destructive interference occurs
Explanation:
Given that two waves are traveling towards each with same magnitude of amplitude .
As we know that when two waves are superimpose then
1. If they are traveling in the same direction then the resultant wave amplitude is higher than the amplitude of any the given wave and this is known as constructive interference.
2. If they are traveling in the opposite direction then the resultant wave amplitude is lower than the amplitude of any the given wave and this is known as destructive interference.
So the answer is a.
a) destructive interference occurs
As the box is moving with a constant velocity, the two forces acting on the box are canceling each other.
Then friction force = 80 Newtons but in the opposite direction.
Friction force = Mu * Normal force exerted by ground = Mu * weight of box
So we find Mu.
Mu = coefficient of friction between box and horizontal surface
= Force of friction / weight = 80 / 50 * 9.81 = 0.163
When an identical box is placed on top, the force of friction is
= Mu * total weight = 0.163 * (50+50) * 9.81 = 159.9 Newtons