THE NATURE OF FORCE & MOTION



THE NATURE OF FORCE & MOTION

Motion is the change in position of an object.

A Force is a pushing or pulling action that may result in motion. There can be any number of forces exerted on an object.

The Net Force is the overall force on an object.

When there is a net force acting on an object, the force is said to be unbalanced. An unbalanced force on an object will change the object’s motion.

Equal forces acting on an object in opposite directions are called balanced forces. Balanced forces will not change the object’s motion.

Balanced & Unbalanced Forces

Forces Can Combine

+ = = Net Force = 0

Unbalanced Force

Forces Can Cancel Each Other Out

+ = 0 Net Force = 0

Balanced Force

Forces Can “Subtract” From Each Other

+ = = Net Force = 0

Unbalanced Force

Galileo Galilei (1600’s) stated that whether at motion or rest, every object resists any change to its motion. This resistance is called inertia. Inertia is the tendency of an object to resist any change in its motion.

Sir Isaac Newton restated Galileo’s idea in the first of his 3 laws of motion.

Newton’s First Law of Motion: An object at rest will remain at rest, and an object moving at constant speed will continue moving at constant speed unless acted upon by an unbalanced force. Newton’s first law is also call the law of inertia. (Can you explain why?)

Mass is the amount of matter in an object. The SI unit is gram (or kilogram). Remember 1kg = 1,000 grams.

The amount of inertia an object has depends on its mass. The greater the mass of an object, the greater its inertia. So, mass can be defined as a measure of the inertia of an object.

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