To develop this problem it is necessary to apply the concepts related to Sound Intensity.
By definition the intensity is given by the equation

Where,
I = Intensity of Sound
= Intensity of Reference
At this case we have that 15 engines produces 15 times the reference intensity, that is

And the total mutual intensity is 100 dB, so we should




Therefore each one of these engines produce D. 88dB.
Answer:
As the person moves down the zip wire, her increase in kinetic energy is less than her decrease in gravitational potential energy.
Explanation:
Work is done against the air resistance, causing thermal energy to transfer to the surroundings
Answer:
Part a)

Part b)

Explanation:
Part a)
Electric field due to large sheet is given as







now the electric field is given as


Part b)
Now since the electric field is required at same distance on other side
so the field will remain same on other side of the plate

Answer:
8.67807 N
34.7123 N
Explanation:
m = Mass of shark = 92 kg
= Density of seawater = 1030 kg/m³
= Density of freshwater = 1000 kg/m³
= Density of shark = 1040 kg/m³
g = Acceleration due to gravity = 9.81 m/s²
Net force on the fin is (seawater)

The lift force required in seawater is 8.67807 N
Net force on the fin is (freshwater)

The lift force required in a river is 34.7123 N