Reproduction in animals — Science STD 8 — Question

Name a fossil fuel other than coal and petroleum.

How can you show that a sounding tabla is vibrating?

How does a sound making object differ from one that is silent?

Which force is responsible for the wearing out of car tyres?

When a pencil cell is released from a certain point on an inclined wooden board, it travels a distance of 35 cm on floor A before it comes to rest. When the same pencil cell is released from the same point on the same inclined board, it travels a distance of 20 cm on floor B before coming to rest. Which floor, A or B, offers greater friction? Give reason for your answer.

What is meant by 'rolling friction'?

Large scale deforestation leads to the decrease in the amount of gas A in the atmosphere whereas the amount of gas B increases. The increased amount of gas B in the atmosphere causes an effect C which leads to excessive heating of the earth and its atmosphere producing an undesirable phenomenon D. What is A, B, C and D?

What is the length of vocal cords in a man?

Name any four diseases which can be prevented by vaccination.

What is meant by rapid combustion? Give one example of rapid combustion.