Question

The sound intensity from a jack hammer breaking concrete is 2.00 W/m2 at a distance of 2.00 m from the point of impact. This is sufficiently loud to cause permanent hearing damage if the operator doesn't wear ear protection. What is the sound intensity for a person watching from "20".0 m away?

Answer 1

`0.02W/m^2`

Step-by-step explanation:

We are given that

Sound intensity,
`I_0=2W/m^2`

Distance,r=2 m

We have to find the intensity of sound for a person watching from 20 m away.

r'=20 m

`(I)/(I_0)=(r^2)/(r'^2)`

`(I)/(I_0)=(2^2)/((20)^2)`

`I'=I_0((4)/(400))`

`I=2* \frac{100}`

`I=0.02 W/m^2`

Hence, the sound intensity for a person watching from 20 m away=
`0.02W/m^2`

Answer 2

Step-by-step explanation:

We know that intensity of sound is inversely proportional to square of distance of point from the source .

For two points at distance of R₁ and R₂ , Intensity of sound I₁ and I₂ will vary as follows

I₁ / I₂ = R₂² / R₁²

I₁ = 2 W / m² , R₁ = 2 m , R₂ = 20m , I₂ = ?

Putting the values in the expression above

2 / I₂ = 20² / 2²

I₂ = (2 x 4) / 400

= .02 W / m²