Force & Motion Newton’s Laws of Motion

Motion  Motion  An object is in motion if the object changes position relative to a reference point.

Speed with a direction is Velocity  Speed  The speed of an object is the distance it travels divided by the time it takes to travel the distance. Speed = Distance/ Time  Velocity  The speed of an object moving in a particular direction is called its velocity.

Acceleration  Acceleration  The rate at which the velocity of an object changes is called acceleration.

Force is a push or pull exerted on an object. When you exert a force on an object, you can change the object’s motion.  Unbalanced Forces  Cause an object to speed up, slow down, start/stop moving, or change direction.  Balanced Forces  Balanced forces do not change an object’s direction.

Work = Force X Distance  When you exert a force on an object that causes the object to move, you have done work

Introduction to Forces and Motion

Forces at work at an Amusement Park

Potential EnergyPotential Energy  Stored energy  It can be released later to do work  Two types  Gravitational – energy due to position  Example: yo-yo in your hand  Elastic – energy due to compression or stretching.  Example: wound up toy

Kinetic EnergyKinetic Energy  Energy of moving objects  Examples: moving bike, running water

Newton’s First Law: Also Known as “The Law of Inertia” Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.  Inertia put a planet in motion and it will always remain in motion unless an external force acts upon it.  Gravity pulls the planet towards the Sun to keep it in orbit.

Newton's Second Law of Motion:  The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.

Newton's Third Law of Motion:  For every action there is an equal and opposite reaction.  An equal and opposite reaction.