Explanation

Asteroids are also called "minor planets".

They are small, rocky bodies that orbit the Sun, often between Mars and Jupiter.

They are considered remnants from the formation of the solar system and are not large enough to be classified as a planet. 

"asteroids" (possibly what "altereds" was meant to be)

Explanation

Radio waves were first predicted by James Clerk Maxwell in his theory of electromagnetism (Maxwell's equations) in 1867.

Heinrich Hertz experimentally demonstrated their existence in 1887.

Explanation

Signal jammers block or interfere with radio frequencies to stop communication.

They are used for security or preventing unauthorized transmissions.

Explanation

Many handheld metal detectors commonly use 9V batteries, and their operating voltage often falls within the 6V-9V range.

Some sources might mention a lower range like 3-5V for simpler detectors, while others specify a slightly higher range like 7-9V. 

Explanation

 Alexander Graham Bell is credited with inventing the first practical metal detector

He developed it in 1881

Explanation

Handheld metal detectors commonly use batteries ranging from 1.5V (AA) up to 9V.

This low voltage powers the device for portability and safety.

Explanation

Explanation

1. Stone dropped from 400 ft tower — Impact sound heard time:

• What happens: Stone falls, hits water, sound travels back up.

• Key points:

  • Time to fall = $sqrt{frac{2h}{g}} = sqrt{frac{2 times 400}{32}} = 5 text{ seconds}$

  • Time for sound to travel up = $frac{400}{1120} approx 0.36 text{ seconds}$
    

• Total time: Around $5+0.36=5.36$ seconds (approximate).

Explanation

Sound needs a medium (like air, water, or solids) to travel because it moves by vibrating particles.

In a vacuum, there are no particles to vibrate, so sound cannot travel and no sound can be heard.

Explanation

The velocity of sound is calculated using the formula:

Velocity=Frequency×Wavelength

Given:

Frequency = 300 Hz

Wavelength = 4 ft

Velocity=300×4=1200 ft/sec