State Newton's first law of motion. Why is it called the law of inertia? Give two examples of inertia from daily life.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · State the law. A body stays in its state of rest, or of uniform motion in a straight line, unless an unbalanced force acts on it.
2 · Define inertia. Inertia is the tendency of a body to resist any change in its state of rest or motion. Mass is its measure.
3 · Link the two. The first law says bodies resist change on their own, which is inertia. So it is called the law of inertia.
4 · Give two examples.
Inertia of rest: you fall backward when a bus starts suddenly.
Inertia of motion: you fall forward when a moving bus stops suddenly.
5 · Close in one line. So only an unbalanced force can change the rest or motion of a body.
Scoring tip: Write 'unbalanced force' and 'uniform motion in a straight line' in full. Give one example of inertia of rest and one of inertia of motion.
