Download Aptitude Crack
img not found img not found

SI Units - Engineering

Q1:

The bar used for defining the standard metre at the International office of weights and measures at Sevres near Paris, is composed of

A 50% platinum and 50% iridium

B 60% platinum and 40% iridium

C 70% platinum and 30% iridium

D 80% platinum and 20% iridium

E 90% platinum and 10% iridium

ANS:E - 90% platinum and 10% iridium

The International Prototype Kilogram stored in a vault in Paris, was replaced by a formula using Planck's constant in 2019. The IPK was losing mass so the metrology community redefined the kilogram with the aid of the Planck constant.

The IPK is a roughly golf-ball-sized object made of a platinum alloy known as "Pt/'10Ir", which is 90% platinum and 10% iridium (by mass) and is machined into a right-circular cylinder with a height equal to its diameter of about 39 millimeters to reduce its surface area.