Tag: science & technology

Rakesh Sharma became the first Indian citizen to travel to space in 1984 aboard the Soviet spacecraft Soyuz T-11. Kalpana Chawla and Sunita Williams were of Indian origin but were American citizens when they flew in space. The question asks for the first 'Indian person', which refers to Indian citizenship, making Rakesh Sharma the correct answer.

The liver is the second-largest organ in the human body after skin (which is the largest overall). It is also the largest internal organ, performing vital metabolic functions. The heart, brain, and spleen are not the second-largest.

Tooth enamel is the hardest substance in the human body, rating 5 on the Mohs scale. It is primarily composed of hydroxyapatite minerals, making it harder than bones, bone marrow, or nails.

A synapse is the junction between two nerve cells (neurons) where electrical signals are converted to chemical signals via neurotransmitters. It is not related to the bile duct, blood vessels, or heart chambers.

The lateral and medial menisci are crescent-shaped fibrocartilage structures located in the knee joint. They act as shock absorbers and stabilize the knee. They are not found in the foot, brain, or heart.

Gingivitis is inflammation of the gums (gingiva), caused by plaque buildup. It specifically affects gum tissue, not lips, toes, or fingernails. Good oral hygiene prevents and treats gingivitis.

Lithium has the lowest atomic mass (6.94) among the metal options provided, making it the lightest metal in this list. Hydrogen is actually the lightest element overall but isn't among the choices.

Quartz is the crystalline form of silica (silicon dioxide, SiO2) found abundantly in nature. Diamond, ruby, and emerald are different minerals with distinct chemical compositions - diamond is pure carbon, ruby is aluminum oxide with chromium, emerald is beryl.

Speed is defined as the rate of change of distance over time (speed = distance/time). Velocity includes direction, force causes acceleration, and energy is the capacity to do work - none of these measure "how quickly an object moves over a certain distance".

pH measures the concentration of hydrogen ions (H+) in a solution on a logarithmic scale from 0-14. It indicates acidity or alkalinity - lower pH means higher H+ concentration (more acidic), higher pH means lower H+ concentration (more basic).