To solve the problem it is necessary to apply the concepts related to sound intensity. The most common approach to sound intensity measurement is to use the decibel scale:

Where,
is a reference intensity. It is the lowest or threshold intensity of sound a person with normal hearing can perceive at a frequency of 1000 Hz.
I = Sound intensity
Our values are given by,


For each auto the intensity would be,




Therefore the sound intesity for the 7 autos is


The sound level for the 7 cars in dB is


Answer:
1020g
Explanation:
Volume of can=

Mass of can=80g=
1Kg=1000g
Density of lead=
By using 
We have to find the mass of lead which shot can it carry without sinking in water.
Before sinking the can and lead inside it they are floating in the water.
Buoyancy force =

Where
Density of water
Mass of can
Mass of lead
Volume of can
Substitute the values then we get




Hence, 1020 grams of lead shot can it carry without sinking water.
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Answer: For ideal machine efficiency = 1. Hence M.A = V. R. The V. R of an ideal machine and the practical machine is a constant or is the same for both
Answer:
A solenoid is a device comprised of a coil of wire, the housing and a moveable plunger (armature). When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. More simply, a solenoid converts electrical energy into mechanical work.
Explanation:
The coil is made of many turns of tightly wound copper wire. When an electrical current flows through this wire, a strong magnetic field/flux is created.
The housing, usually made of iron or steel, surrounds the coil concentrating the magnetic field generated by the coil.
The plunger is attracted to the stop through the concentration of the magnetic field providing the mechanical force to do work.