Natural Resources — Science STD 9 — Question

Explain why, if we strike a table lightly, we hear a soft sound but if we hit the table hard, a loud sound is heard.

Distinguish between the following pairs in one or two sentences for each: Tendon and ligament.

A moving bicycle comes to rest after sometime if we stop pedalling it. But Newton’s first law of motion says that a moving body should continue to move for ever, unless some external force acts on it. How do you explain the bicycle case?

According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.

Do action and reaction act on the same body or different bodies? How are they related in magnitude and direction? Are they simultaneous or not?

Name two factors on which shape of the cell depends.

What does the diffusion of gases tell us about their particles?

Why does a gas fill a vessel completely?