Sound — PHYSICS STD 9 — Question

What is the nature of the mirror having a focal length of -20 cm?

The table below shows the distance travelled by two vehicles A and B during each second:

Time (s)	0	1	2	3	4	5	6	7
Distance travelled by A (m)	0	20	80	180	240	300	360	420
Distance travelled by B (m)	0	10	40	90	160	250	360	490

At what time do A and B meet?Which vehicle is moving with a constant acceleration?

Give reasons for the following:
In cold countries, water pipes burst in winter.

Name the instrument used to control the current in an electric circuit.

State the effect of green house gases on the temperature of earth's atmosphere.

Name an instrument used to measure the mass of a body.

'The resistance of a wire is 2 ohm'. Explain the meaning of this statement.

How will you plot the magnetic field lines by using a small compass needle?

A body falls towards the earth. Does it have positive or negative acceleration?

Is sound a form of energy?