Why Do we Fall Ill — Science STD 9 — Question

Classify the following into metals, non-metals and metalloids: Silicon, Mercury, Diamond, Sulphur, Iodine, Germanium, Sodium, Carbon, Magnesium, Copper, Boron, Helium.

A boy tries to push a truck parked on the roadside.The truck does not move at all. Another boy pushes a bicycle moves through a certain distance. In which case was the work done more: on the truck or on the bicycle? Give a reason to support your answer.

How are diseases transmitted in crops?

Which molecules are present in chromatin.

Identify the animal tissues from the given descriptions and also mention their location in the human body.
Tissue A cells are filled with fat globules and the tissue acts as an insulator.

Mention three effects of excessive irrigation

Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions.

Define velocity. What is the SI unit of velocity?