**Herong's Notes on Physics** - Version 3.21, by Dr. Herong Yang

Newton's Second Law of Motion

This section introduces Newton's Second Law of Motion - The acceleration of an object is directly proportional to the net force acting on the object, and inversely proportional to the mass of the object.

Newton's Second Law of Motion - The acceleration of an object is directly proportional to the net force acting on the object, and inversely proportional to the mass of the object.

Newton's second law of motion can also be expressed as a formula: F = ma, where F represents the net force, m represents the mass of the object, and a represents the acceleration. The standard units of measure used in this formula are:

F (force): newton m (mass): kilogram (kg) a (acceleration): meter per second per second (m/s/s/)

Can a human pull an airplane to accelerate? Yes, Kevin Fast from Canada was able to pull and accelerate airplane of 188,000kg. If we assume that Kevin Fast can give the airplane a constant net force of 1,000 newtons, the airplane will be accelerated at 0.00532m/s/s constantly.

How far can Kevin pull the airplane after 60 seconds (1 minute)? The answer can be calculated with the following steps:

Initial speed is 0.0m/s Acceleration is 0.00532m/s/s Final speed at 60s time is 0.31915m/s Average speed is 0.159574m/s Distance at 60s time is 9.57447m

So Kevin can pull the airplane for almost 10 meters with 60 seconds!

Actually, Newton's First Law of Motion is a special case of the Second Law of Motion, where F is 0.

*Last update: 2014.*

Table of Contents

Introducion of Frame of Reference

►Newton's Second Law of Motion

Falling Ball in Earth Frame of Reference

Falling Ball in Elevator Frame of Reference

Introduction of Special Relativity

Time Dilation in Special Relativity

Length Contraction in Special Relativity

The Relativity of Simultaneity