Explanation

Marble is a type of metamorphic rock formed when limestone is subjected to heat and pressure.

It is commonly used in building and decoration due to its strength and appearance.

Explanation

An airplane's wings are shaped to push air downward, which creates an upward force called lift.

This lift balances the force of gravity, allowing the plane to stay in the air.

Explanation

Pakistan's National Space Agency SUPARCO.

SUPARCO stands for Space and Upper Atmosphere Research Commission.

SUPARCO was set up in 1961.

Explanation

• Apollo 17 was the manned spacecraft that took humans to the moon.
• Apollo 17 was the sixth and final Apollo mission to land on the Moon.
• It was crewed by astronauts Eugene Cernan, Ronald Evans, and Harrison Schmitt.

Explanation

Direct current is produced when electrons flow constantly in one direction.

It's abbreviated as "DC".

Since direct current flows in one direction only, its electrical pressure or voltage is always oriented in one direction, or "polarity".

Explanation

Electronics is the branch of science that studies the flow and control of electrons, especially in circuits.

It uses active devices (like transistors and diodes) to control electron flow through amplification and rectification.

Explanation

Explanation

To find the harmonic that is two octaves higher in pitch than the fundamental, we need to consider the frequency multiplication.

One octave higher = 2 × fundamental frequency

Two octaves higher = 2 × 2 × fundamental frequency = 4 × fundamental frequency

The fourth harmonic has a frequency four times the fundamental frequency, which corresponds to two octaves higher.

Explanation

Pneumatic systems are used in:

• Spray guns (to atomize and spray paint or other materials)
• Pumps (to compress and transfer fluids)
• Vacuum cleaners (to create suction and lift dust and debris)
• Dental drill or dentistry tools (to power drills, sanders, and other instruments)

Explanation

A reflecting telescope uses two mirrors:

1. The primary mirror (which collects and focuses light).
2. The secondary mirror (which directs the focused light to the eyepiece), to form an image of distant objects.