Is Matter Around Us Pure ? — Science STD 9 — Question

Give an example in which physical and chemical changes take place together.

In an experiment, 1.288g of barium sulphate was obtained from 1.03g of barium. In another experiment, 3.672g of barium sulphate gave, on reduction, 2.938g of barium. Show that these figures verify the law of constant proportions.

Write the formula to calculate the speed of a body moving along a circular path. Give the meaning of each symbol which occurs in it.

What is meant by (i) elements (ii) compounds, and (iii) mixtures? Write down the names of two elements, two compounds and two mixtures.

A piece of stone is thrown vertically upwards. It reaches the maximum height in 3 seconds. If the acceleration of the stone be 9.8m/s² directed towards the ground, calculate the initial velocity of the stone with which it is thrown upwards.

A ball thrown up vertically returns to the thrower after 6s. Find the maximum height it reaches.

Explain why it is possible for a small animal to fall from a considerable height without any injury being caused when it reaches the ground.

A weightlifter is lifting weights of mass 200kg up to a height of 2 metres. If g = 9.8ms^-2, Calculate:

1. Potential energy acquired by the weights.
2. Work done by the weightlifter.

Define intercropping. How does it differ with mixed cropping?