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

A sound signal of 128 vibrations per second has a wavelength of 2.7m. Calculate the speed with which the wave travels.

How much water should be mixed with 12ml of alcohol so as to obtain 12% alcohol solution?

Explain why, the motion of a body which is moving with constant speed in a circular path is said to be accelerated.

A bulb lights up when connected to a battery. State the energy change which takes place:

1. In the battery.
2. In the bulb.

A train starting from stationary position and moving with uniform acceleration attains a speed of 36km per hour in 10 minutes. Find its acceleration.

A sonar station picks up a return signal after 3 seconds. How far away is the object? (Speed of sound in water = 1440m/s).

Give two reasons for supposing that water is a compound and not a mixture.

A car is moving on a level road. If the driver turns off the engine of the car, the car’s speed decreases gradually and ultimately it comes to a stop. A student says that two forces act on the car which bring it to a stop. What could these forces be? Which of these two forces contributes more to slow down and stop the car?

1. Compare the properties of solids, liquids and gases in tabular form.
2. Give two reasons for saying that wood is a solid.

During class, the students resemble molecules in a solid (because they are very close to one another)

While going from one classroom to another the students resemble molecules in a liquid (because they are a little more father apart from one another)