NEWTON'S 3 LAWS OF MOTION
NEWTON'S 1st LAW
The general meaning of Newton's 1st law is that an object will continue doing what it is doing unless an outside force acts upon it.
​
The force of gravity on an object is called its weight.
weight = mass * gravity
w = m * g
NEWTON'S 2nd LAW
Newton's second law states that a net force applied to an object causes acceleration.
​
A larger mass will cause a lesser acceleration while a lar​ger force will cause a greater acceleration.
mass * acceleration = net force
m * a = Fnet
Force is measured in Newtons (N)
Inertia is an objects resistance to a change in motion. Newton's 1st law is based on inertia.
​
Mass affects the inertia of an object meaning that a heavier object would resist change in motion more that a lighter object would.
​
For examples of inertia view this video:
​
Inertia
Examples
A soccor ball will not move unless a player kicks it.
​
Crashing a bike into a rock will send the person forward.
​
Attempting to move a monster truck with only your strength.
Net Force
Throwing a bowling ball would take more effort than a tennis ball.​
​
Pushing a toy car and a real car with the same force will cause a much greater acceleration to the toy car​.
​
One boy can kick a soccer ball further than another if he uses a greater force.
Examples
A net force is the result of more than one force acting on the object.
​
If the Net Force is positive then the applied force is greater than the friction force and the object is speeding up.
If the Net Force is negative then the friction force is greater than the applied force and the object is slowing down.
If an object is moving at a constant velocity that means the friction force is equal to the applied force.
​
Friction is present whenever any two objects are interacting
Free Body Diagrams
Free body diagrams are used to show the forces acting on an object.
​
The object is always represented with a box and the forces are shown by vectors.
The length of a vector relates to the magnitude of the force. Forces shown include gravitational, applied, friction, normal, tension, and spring.
​
"Free Body Diagram Interactive." Free Body Diagram Interactive. Physics Classroom, Web. 02 June 2016.
NEWTON'S 3rd LAW
Newton's third law states that for every action there is an equal and opposite reaction.
​
This means that a mosquito and a windshield would apply the same force to each other.
​
Although this is true, the mosquito would then experience a greater acceleration because of its smaller mass.
Because this can be a difficult concept to understand, it can be represented with the equation.
A greater mass will experience a lesser acceleration than a smaller mass with the same force being applied.
​
acceleration = Fnet / mass
acceleration = Fnet / mass
Examples
A bug hitting a moving car's windsheild (they would apply the same force to eachother but the bug would be squashed due to the large and rapid change in acceleration).
​
A cannon being fired. The cannon ball will be shot but it will apply the same force it is reciving to the cannon. The cannon expirences less acceloration because it's heavier.
​
A rocket launching. The rocket propells air and fuel out the bottom, the air pushes the rocket upwards.
