List of top Science Questions

Fill in the blanks with suitable words.

1. Time taken by an object to complete one oscillation is called ___ .
2. Loudness is determined by the ___ of vibration.
3. The unit of frequency is ___.
4. Unwanted sound is called __________ .
5. Shrillness of a sound is determined by the ___ of vibration.

Voice of which of the following is likely to have minimum frequency?

Choose the correct answer.
Sound can travel through

Explain why objects moving in fluids must have special shapes.

Give examples to show that friction is both a friend and a foe.

Explain why sportsmen use shoes with spikes.

Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.

Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be

Fill in the blanks.

1. Friction opposes the ___ between the surfaces in contact with each other.
2. Friction depends on the ___ of surfaces.
3. Friction produces ___.
4. Sprinkling of powder on the carrom board ___ friction.
5. Sliding friction is ___ than the static friction.

When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to

A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?

In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

What are sex hormones? Why are they named so? State their function.

Does pure water conduct electricity? If not, what can we do to make it conducting?

A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that

Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them.

Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reasons?

Name three liquids, which when tested in the manner shown in Fig.11.9, may cause the magnetic needle to deflect.

List changes in the body that take place at puberty.

Explain the process of formation of petroleum.

Explain why fossil fuels are exhaustible natural resources.

Suppose you are outside your home and an earthquake strikes. What precaution would you take to protect yourself?

Describe how coal is formed from dead vegetation. What is this process called?

List three states in India where earthquakes are more likely to strike.