Title Advanced series 7th class Physics - Solutions.pdf ✅

Class 7 – Physics | A - 7 Units and Measurements 1 1. Units and Measurements Solutions • Physical Quantity • Fundamental Physical Quantity, Derived Quantity • Unit • System Of Units • Guidelines For Writing Units LEVEL-I 1. Correct option: (A) To know and understand a physical situation completely, one is likely to measure the quantities such as distance, speed, time, mass, acceleration, force etc. which are called the physical quantities. Physical quantity is that in terms of which laws of physics can be expressed and which can be measured directly or indirectly. 2. Correct options: (A, B, C) Fundamental quantities are the quantities whose measurement is done with the independent units. The quantities in option (D) Length, time and mass are measured by independent units such as kilogram, meter and second respectively. In all the other options velocity is there which is expressed in terms of derived units which is meters per second. So, all the other sets cannot enter into the list of fundamental quantities in any system of units. 3. Correct option: (B) Mass is a physical quantity as it is used to measure a physical situation. Rest all are the emotional situations 4. Correct option: (A) Fundamental physical quantities are the quantities whose measurement does not depend on other physical quantities. For example, quantities Length, time and mass are measured independently and hence they are fundamental physical quantities. 5. Correct option: (B) Derived quantity is a quantity whose measurement is done with the help of other physical quantities and it can be obtained by writing the defining equation in terms of fundamental physical quantities. For example, velocity is a derived physical quantity which depends on fundamental quantities distance(length) and time. 6. Correct option: (B) Measurement is basically a comparison process. It involves the selection of a unit of measurement and comparing the quantity with standard unit. The standard chosen should be of the same nature as that of the quantity to be measured. For example, if we have to measure the length of a rod, we have to take length as the standard quantity.