Newton's First Law Flashcards

All 6 cards in this deck

State Newton's first law.

An object stays at rest, or keeps moving at a constant velocity, unless a resultant force acts on it.

What is the resultant force on a body moving at a constant velocity?

Zero — the forces on it are balanced.

What happens to the motion of a body when the resultant force on it is not zero?

Its speed and/or its direction changes, i.e. it accelerates in the direction of the resultant force.

True or false? A moving object needs a resultant force acting on it to keep moving at a steady speed in a straight line.

False. With zero resultant force it carries on at constant velocity; a force is only needed to change the motion.

True or false? A resultant force can change the direction of a body without changing its speed.

True. A change of direction is a change of velocity, e.g. an object moving in a circle at constant speed.

What is the name for the state of an object when all the forces on it are balanced?

Equilibrium — the resultant force is zero, so it is at rest or moving at constant velocity.