NEET Practice Questions (MCQs) with Answers & Solutions

A tin cry is the characteristic sound heard when a bar of tin is bent. Variously described as a "screaming" or "crackling" sound, the effect is caused by the crystal twinningin the metal. The sound is not particularly loud, despite terms like "crying" and "screaming". It is very noticeable when a hot-dip tin coated sheet metal is bent at high speed over rollers during processing.

The tin cry is often demonstrated as a simple science experiment. The bar of tin will "cry" repeatedly when bent until it breaks. The experiment can then be recycled by melting and recrystallizing the metal. The low melting point of tin (only 232 °C, or about 500 K) makes re-casting easy. Tin anneals at reasonably-low temperature as well, normalizing tin's microstructure of crystallites/grain

Carbogen, also called Meduna's Mixture after its inventor Ladislas Meduna, is a mixture of carbon dioxide and oxygen gas. Meduna's original formula was 5% CO₂ and 95% oxygen, but the term carbogen can refer to any mixture of these two gases, from 1.5%^[1] to 50%^[2] CO₂.

A carbogen mixture of 95% oxygen and 5% carbon dioxide can be used as part of the early treatment of central retinal artery occlusion.

Carbogen is used in biology research to study in vivo oxygen and carbon dioxide flows,^[6] as well as to oxygenate the aCSF solution and stabilize the pH to about 7.4 in research on acute brain slices.

Its use in combination with nicotinamide is also being investigated in conjunction with radiation therapy in the treatment strategy of certain cancers.^[7] Because increased tumor oxygenation improves the cell-killing effects of radiation, it is thought that the inhalation of these agents during radiation therapy could increase its effectiveness.

Bullet of gun possesses lead in it.

Lead disrupts the activities of almost all enzymes but most importantly,the activity of the enzyme involved in the production of haem for haemoglobin in red blood cells. ... Lead can also damage the nerves

Bullets are cylinders that contain a packing of black powder and a primer to create a spark to start the reaction. Once the reaction begins, the gases that are produced build up rapidly and then eject the projectile from the front of the bullet. The part of the bullet left behind is called the cartridge.

The projectile is fired at a rate of 120 m/s to 1700 m/s depending on the type of gun and powder used. The rate at which a projectile leaves a gun is called its Muzzle Velocity.

At the other end of the firing of a bullet is the poor fellow that gets hit with the projectile. The wound that is received is called ballistic trauma.

Ballistic Trauma

The degree of tissue disruption caused by a projectile is related to the size of the cavity it creates as it passes through the body. The extent of cavitation (the hole it makes) is related to the following characteristics of the projectile:

1. The kinetic energy (KE) of the bullet (KE = ½(mass)(velocity)²)
2. The Yaw (spinning movement)
3. Deformation (how flattened or squashed it is)
4. Fragmentation (how many pieces it breaks into)

Generally, the faster the bullet travels or the larger it is, the greater the damage. Once the bullet strikes the body the primary cause of death is blood loss, the secondary cause is shock.

Graphite is good conductor of current.

Pb forms only one hydride as ${\mathrm{PbH}}_4$. Sn forms only two hydrides as ${\mathrm{SnH}}_4$ and ${\mathrm{Sn}}_2{\mathrm{H}}_6$. Rest all forms number of hydrides.

The stability of group 14 tetrahalides decreases down the group whereas of dihalides increases down the group.

 a polymeric structure.

${\mathrm{PbO}}_2 + 2{\mathrm{HNO}}_3 \stackrel{ }{\to } \mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2 + {\mathrm{H}}_2\mathrm{O} + \frac{1}{2}{\mathrm{O}}_2$

B(OH)₃ is ortho boric acid