"An organ pipe is 1.5 m long and closed at one end. What are the first three harmonic frequencies of this pipe?"

57.2 Hz, 171.5 Hz and 285.8 Hz

Explanation:

In a pipe, an open end has antinodes while closed ends have nodes.

The distance is between a node and an antinode is an odd multiple of one-quarter of a wavelength.

For the first harmonic,

Also,

where f is the frequency and v is the velocity.

Substitute the value of .

For the second harmonic,

For the third harmonic,

first harmonic = 56.7 Hz

Third harmonic = 170 Hz

Fifth harmonic = 283.3 Hz

Explanation: see attachment

an obstruction

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.