Answer:
1.4E-3J
Explanation:
Given that
Time = 8hrs = 28.8E3 seconds
Intensity= 90dB
D= 0.008m
Radius= 0.004m
So intensity is sound level Bis
10dBlog(I/Io)
I= 10 (B/10dB)Io
= 10( 90/10) x 10^-12
=0.001W/m²
But we know that
I = P/A
P= I πr²
= 5.02 x10^-8W
But energy is power x time
So E= 5.02E-8 x 28.8E3
= 1.4E-3J
Force bc it says the ability to make stuff happen
Answer:
a

b

Explanation:
From the question we are told that
Their distance apart is 
The wavelength of each source wave 
Let the distance from source A where the construct interference occurred be z
Generally the path difference for constructive interference is

Now given that we are considering just the straight line (i.e points along the line connecting the two sources ) then the order of the maxima m = 0
so

=> 
=> 
Generally the path difference for destructive interference is

=> 
=> 
substituting values

=> 
So


and

=> 
=> 
Answer:
24,187.04 J ≈ 24,200 J
Explanation:
mass (m) = 544 kg
initial speed (u) = 6.75 m/s
final speed (v) = 15.2 m/s
change in height (Δh) = -14 m (negative sign is because there is a decrease in height )
acceleration due to gravity (g) = 9.8 m/s^{2}
How much work was done on the raft by non conservative forces?
work done = change in energy of the system = change in kinetic energy + change in potential energy
work done = (
) + (mgΔh)
work done = (
) + (544 x 9.8 x (-14))
work done = 50449.76 - 74,636.8
work done = 24,187.04 J ≈ 24,200 J