General Science GK Questions with Answers – Page 79

Common solder is an alloy of lead (Pb) and tin (Sn), often in a ratio close to 40:60. Solder is used to join metal parts, especially wires and components in electrical circuits.

Doubling one mass doubles the force, while doubling the distance cuts it to one-fourth, so the net result is 2 × 1/4 = 1/2.

120 mmHg is the systolic pressure when the ventricles contract, and 80 mmHg is the diastolic pressure when they relax.

The endodermis is the innermost layer of the cortex that surrounds the vascular tissue; it is not a part of the vascular bundle itself.

Chess skill is an acquired trait, built by learning and practice, and acquired traits are not passed on through genes.

The equation v = u + at has the form y = c + mx, so the graph is a straight line that cuts the velocity axis at u and has slope a. On a velocity-time graph, time is on the x-axis and velocity on the y-axis.

The apical meristem at the tip of the stem and root makes new cells that increase the plant's length, so damage to it stops growth in length.

Marsilea is a water fern, a pteridophyte, and pteridophytes are the first land plants with true vascular tissues, xylem and phloem.

An LED is a p-n junction diode that gives out light when current flows through it in the forward direction.

By Coulomb's law the force F = kq₁q₂/r² comes out positive, meaning repulsive, whenever the two charges have the same sign.

To see one's full image in a plane mirror, the mirror must be at least half the person's height: half of 1·5 m is 0·75 m. Light from Sita's feet must reflect from the mirror into her eyes, and so must light from the top of her head.

Physics recognises four fundamental forces: gravitational, electromagnetic, strong nuclear and weak nuclear, and the question lists all four. Every other force we meet is a form of these.

Adenosine triphosphate is the energy currency of the cell: breaking its last phosphate bond releases energy for cell work. ATP is made mainly in the mitochondria during cellular respiration, and in the chloroplasts of green plants during photosynthesis.

Force depends on how fast momentum changes, not on the momentum itself. Newton's second law states that the rate of change of momentum of a body is proportional to the net force on it and takes place in the direction of the force.

If pressure is proportional to temperature for a fixed amount of ideal gas, the volume must stay constant, so the process is isochoric.

Mass is the same everywhere, but weight changes with g, so only statement II holds. Inertial mass measures how much a body resists a change in motion (F = ma); gravitational mass measures how strongly gravity pulls it.

A mirage forms when light from the sky bends through hot, less dense air near the ground and is finally totally internally reflected.

Constant velocity means both the speed and the direction stay the same, so the speed cannot change. Velocity is a vector: it has a magnitude, the speed, and a direction.

The pericycle is a layer of cells around the vascular cylinder of the root and stem; it is not part of xylem or phloem.

Radiant heat is infrared electromagnetic radiation, so it travels in straight lines at the speed of light. Heat moves in three ways.