Diversity In Living Organisms — Science STD 9 — Question

A ball is thrown vertically upwards with a velocity of 49m/ s. Calculate

1. The maximum height to which it rises
2. The total time it takes to return to the surface of the earth.

Find the velocity with which a ball is thrown up if it reaches the maximum height in 5s. Also find its maximum height.

What is biological control?

Cinnabar (HgS) is a prominent ore of mercury. How many grams of mercury are present in 225g of pure HgS? Molar mass of Hg and S are 200.6g mol^–1 and 32g mol^–1 respectively.

Name the distinctive features of complex plants, that helped in their survival on the Earth.

Which of the following are physical changes and which are chemical changes?
Burning of candle wax, Melting of candle wax, Mixing of iron filings and sand, Burning of wood, Breaking a piece of chalk, Burning a piece of paper, Cutting a piece of paper.

Two different bodies are completely immersed in water and undergo the same loss in weight. Is it necessary that their weights in air should also be the same? Explain.

Give reason for the following observations.
Naphthalene balls disappear with time without leaving any solid.