- it is very useful to have two units for the amount of substance i.e , kilogram and the mole.if we want to consider a specific amounts of mass without considering number of microscopic atoms present in it, it is useful to use kilogram . because one kilogram of different Substances contains different number of molecules . while if we want to consider a fixed number of atoms present in it then it is useful to use mole.because one mole of any substance contains the same number of atoms or molecules.*. An old saying is that 'A chain is only as strong as it as its weakest link ' , what analogue statement can you make regarding experimental data used in computation: ? "the analogue statement regarding experimental data used in computation ' A result obeained from an experimental data used in computation is only as as accurate as its least accurate reading. ". An object is thrown vertically upward.Discus the sign of acceleration due to gravity, relative to velocity , while the object is in air : ? "when an object is thrown vertically upward the sign of acceleration due to gravity is negative relative to velocity. But when the object is thrown downward, the sign of acceleration due to gravity is taken as positive because velocity and acceleration are in the same direction.". projectile motion: ? "when an object is thrown in air making a certain angel with horizontal, So that object moves under the action of gravity and moves along a corved path is called as projectile . its motion is called projectile motion . its path is called Trajectory.its path is called parabolic."
