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

Define the following terms.
Valency.

A bowler runs a long distance before bowling from the bowling line. Why?

In which class would you place any organism which has:

1. A scaly exoskeleton and a bony endoskeleton.
2. A scaly exoskeleton and lay eggs outside water?

Under what conditions can a body travel a certain distance and yet its resultant displacement be zero?

Give one example where:
A force moves a stationary body.

Does the motion of second’s hand of a watch represent uniform velocity or uniform speed?

What changes continuously in uniform circular motion?

Name the technique to separate butter from curd.

Name these force:
The force which wears away two surfaces as they move over one another.