The bus jerk
A law is a pattern that happens every time.
Standing in a bus
You stand in a bus without holding on. The driver brakes suddenly.
What happens to you?
What this lesson covers
The idea
A law describes a regular pattern observed in nature, often expressed in words or as a mathematical relationship.
Standing in a bus
You stand in a bus without holding on. The driver brakes suddenly.
What happens to you?
- I lean forward
- I lean backward
- Nothing happens
Try the bus
Brake gently, brake suddenly, and start from rest. Watch the passenger each time.
The pattern is the law
A law describes a regular pattern observed in nature. It is often expressed in words or as a mathematical relationship.
Here the pattern in words: *a moving body keeps moving, and a body at rest stays at rest, unless a force acts on it.* This is part of Newton’s laws of motion. Other laws are written as equations, like Ohm’s law, V = IR, which you will meet later.
- What the bus does | Which way the passenger leans | How much
- brakes | forward | more if sudden
- starts | backward | more if sudden
Notes
A law describes a regular pattern observed in nature, often in words or as a mathematical relationship.
Check yourself
Every time a moving bus brakes suddenly, standing passengers lean forward. What do we call a statement of such a regular pattern?
Which statement is a law-like pattern, not a one-time event?
The bus is at rest and then starts suddenly. Which way do the passengers lean?
A law can be expressed as…
- A law — correct. Yes. A law describes a regular pattern in nature.
- A guess. A law comes from patterns seen again and again.
- A model. A model simplifies a system. A law states a pattern.
- Ravi fell over in the bus today. That is one event. A law is a pattern that repeats.
- Whenever a moving bus brakes suddenly, standing passengers lean forward — correct. Yes. It is a pattern seen again and again.
- The bus was yellow. That is a single fact, not a pattern.
- Forward. Forward is for braking. At a start, the passengers stay behind.
- Backward — correct. Yes. The pattern works both ways: bodies resist a change of motion.
- Sideways. The pattern is along the line of motion.
- only a drawing. Laws are expressed in words or in mathematics.
- words, or as a mathematical relationship — correct. Yes. For example Ohm’s law, V = IR.
- only a single number. A law is a relationship or a pattern, not one number.