Improvement in Food Resources — Science STD 9 — Question

What is green manuring? Give suitable example for green manures.

What are the constituents of phloem?

Would you cool a bucket of water more quickly by placing it on ice or by placing ice in it? Give reasons for your answer.

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.

Calculate the change in momentum of a body weighing 5kg when its velocity decreases from 20m/s to 0.20m/s.

Certain force acting on a 20kg mass changes its velocity from 5m s^–1 to 2m s^–1. Calculate the work done by the force.