ICSE Physics Class 7 Notes Chapter 1 Physical Quantities and Measurement
→ The mass of a body is the quantity of matter contained in a body regardless of its volume or any force acting on it.
→ The weight of a body is the force with which every body is attracted towards its centre.
→ The unit of mass in S.I. system is kilogram (kg).
→ Higher units of mass are quintal and metric tonne.
→ The weight of body changes with acceleration due to gravity.
→ Weight is zero at the centre of the earth.
→ Mass per unit volume of a substance is called density of the body.
→ The unit of density in S.I. system is kg nr3 and gem-3 in C.G.S. system.
→ The density in S.I. system is 1000 x numerical value in C.G.S. system.
→ The density of liquids and gases decreases or increases with the rise or fall in temperature.
→ The cycle of upward and downward movements of the fluid form currents in the medium which are known as convectional currents.