Answer:

Explanation:
Given,
Magnetic field, B = 5 x 10⁻⁵ T
Number of turns, N = 450
length = 29 cm
Current,I = ?
Using formula of magnetic field due to solenoid




Hence, the current obtained is equal to 0.0256 A.
Answer:
Sonar
Explanation:
Sonar is a technique that involves the use of sounds in viewing substances in a water medium to aid movement or communication. It makes use of the advantage of sound waves traveling faster and farther in water when compared to other types of waves such as light waves.
During World War II, the military employed the use of SONAR in imaging the seafloor by sending pulses of sound waves down through the water and measuring the time it took for the sound to bounce off the seafloor and return to the receiver.
Yes spoon can sound like a bell. To prove this, we perform an experiment.The handle of the spoon is tied at the mid point of the string, then wrap the ends of the string around pointer fingers. Now place fingers in ears. Lean over so that spoon hangs freely and swing the spoon so it taps against a door.
A sound is produced because the spoon vibrated, causing sound waves to travel up the string and into ears.
Answer:
f = 276.6 Hz
Explanation:
This musical instrument can be approximated to a tube system where each tube has one end open and the other closed.
In the closed part there is a node and in the open part a belly or antinode. Therefore the wavelength is
L = λ/ 4
speed is related to wavelength and frequency
v = λ f
λ = v / f
we substitute
L = v / 4f
f = v / 4L
the speed of sound at 20ºC is
v = 343 m / s
let's calculate
f =
f = 276.6 Hz
We know, by conservation of energy :

Therefore,

Putting given values, we get :

Therefore, the spring be compressed to 6.93 cm to send the ball twice as high.
Hence, this is the required solution.