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

Explain why, ice at 0°C is more effective in cooling than water at the same temperature.

For how long should a force of 100N act on a body of 20kg so that it acquires a velocity of 100m/s?

A car is moving on a straight road with uniform acceleration. The speed of the car varies with time as follows:

Time (s)	0	2	4	6	8	10
Speed (m/s)	4	8	12	16	20	24

Draw the speed-time graph by choosing a convenient scale. From this graph:

1. Calculate the acceleration of the car.
2. Calculate the distance travelled by the car in 10 seconds.

What is the momentum in kgm/s of a 10kg car travelling at (a) 5m/s (b) 20cm/s, and (c) 36km/h?

What is the difference between speed and velocity?

What do you understand by the term “transformation of energy”? Explain with an example.

What are (i) metals (ii) non-metals, and (iii) metalloids? Give two examples each of metals, non-metals and metalloids.

Give reason for the following:
In most of the cases, we cannot see the vibrations of a sound producing object with our eyes.

State the law of conservation of momentum.

Explain why, osmosis can be considered to be a special kind of diffusion. Classify the following into (i) osmosis, and (ii) diffusion:

1. Swelling up of a raisin on keeping in water.
2. Spreading of virus on sneezing.
3. Earthworm dying on coming in contact with common salt.
4. Shrinking of grapes kept in thick sugar syrup.
5. Preserving of pickles in salt.
6. Spreading of smell of cake being baked in the kitchen.
7. Aquatic animals using oxygen dissolved in water during respiration.