Pressure in Fluids and Atmospheric Pressure — PHYSICS STD 9 — Question

What do you mean by reflection?

Give qualitative definition of force on the basic of Newton's first law of motion.

An object covers a distance of S meters in t seconds as follows :

S (meters)	0	8	20	20	16	10	0
t (Seconds)	80	2	5	10	12	15	10

Plot a graph, taking t on X-axis and S on Y-axis. Determine the velocity of the object at time
(i) 6 s, and
(ii) 14 s.

Define the following term:
Coefficient of cubical expansion

Give a scientific reason for the following:
In winter the birds fluff up their feathers.

A current of 4.5 A flows through a conductor for 2.5 s. What amount of charge passes through the conductor?

What do you mean by an electric current?

'The resistance of a wire is 1 ohm'. Explain the meaning of this statement.

On placing your ear close to an iron railing which is tapped some distance away, sound is heard twice. Explain, why?

Can we subtract a scalar quantity from a vector quantity? Is the reverse true?