The Fundamental Unit of Life — Science STD 9 — Question

Explain why, a runner presses the ground with his feet before he starts his run.

Write two differences between isobars and isotopes. 

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

Define speed. What is the SI unit of speed?

Name any two simple and two complex permanent tissues in plants.

An object is moving along a straight line with uniform acceleration. The following table gives the velocity of the object at various instants of time:

Time (in sec.):	0	1	2	3	4	5	6
Velocity (in m/s):	2	4	6	8	10	12	14

Plot the graph.
From the graph,

1. Find the velocity of the object at the end of 2.5 seconds.
2. Calculate the acceleration.
3. Calculate the distance covered in the last 4 seconds.

What is the atomicity of the following?

1. Oxygen
2. Ozone
3. Neon
4. Sulphur
5. Phosphorus
6. Sodium

When water is cooled to a temperature x, it gets converted into ice at temperature x by a process called P. And when ice at temperature x is warmed, it gets reconverted into water at the same temperature x in a process called Q.

1. What is the value of temperature x in Kelvin?
2. What is the process P known as?
3. What is the name of energy released during process P?
4. What is the process Q known as?
5. What is the name of energy absorbed during process Q?

Define the cell.

A beaker full of water is suspended from a spring balance. Will the reading of the balance change:

1. If a cork is placed in water?
2. If a piece of heavy metal is placed in it?

Give reasons for your answer.