Question

The physical quantity having the same unit in all systems of unit is:
A) Length
B) Mass
C) Time
D) Foot

Answer 1

Here we have to observe all the physical quantities and see what will be the units in SI, FPS, CGS and MKS systems.
Generally the standard unit is taken everywhere.

The International System of Units (SI) is a unit system introduced by the General Conference of Weights and Measures in 1960 and recommended for use in both scientific and technological fields. It consists of seven basic units (metre, kilogram, second, ampere, kelvin, mole, candela) plus derived units and prefixes.

Complete step by step solution:
Centimetre Gram The second unit system (abbreviated CGS or cgs) is a variation of the metric system based on the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time.

MKS is a unit system based on calculating distances in metres, mass in kilogram and time in seconds. MKS is typically used in engineering and starting physics, where the so-called cgs method (based on the centimetre, gram, and second) is widely used in theoretical physics.
The foot pound second system or FPS system is a system of units based on three simple units, foot for length, pound for mass, and second for time. The FPS system is no longer used.

Length: The measurement of distance of dimension of an object is known as length.
Its Standard unit is metre. Its CGS unit is centimetre. The FPS unit is foot and the MKS unit is metre.

Mass: Mass is both the property of the human body and the measure of its resistance to acceleration (change in its state of motion) as the net force is applied.
The S.I unit is kilogram. The CGS unit is gram. The MKS unit is kilogram and the FPS unit is pound.

Time: Physical time is determined by its measurement: time is what the clock reads.
The unit of is the same in every system of measurement. It is measured in seconds.

Thus we can see that option C is correct.

Note:
Although second is the standard unit of measurement now – a – days time is also measured in millisecond, microsecond, minute and hour.