Newtons Second Law of Motion

Define Newtons Second Law of Motion …

The acceleration of an object is directly proportional to the net force acting on the object, inversely proportional to the objects mass, and in the direction of the net force.

What is the subject of the law …

Acceleration

What is the equation of newtons third law …

F=ma and can also be re-arranged as a=f/m

In equation form the second law can be used to …

Find the size of the net force needed to give a certain sized mass a certain amount of acceleration

If the size of the mass you want to accelerate increases …

So does the amount of force required, since more mass means more inertia and more resistance the change in motion more

If the size of the acceleration you want to give a mass increases …

So does the amount of force required, since a bigger change in motion causes more resistance than a smaller change in motion.

What is the definition of Force …

What must act on an object in order to change its motion or the resistance an object offerst to changes in motion

what does the magnitude of force depend on …

The size of the force it takes to accelerate and object depends upon how much the object resists changes in motion

What magnitude should the force have to accelerate an object ?

Since the resistance that an object offers depends on two things, mass and inertia, in order for a net force to accelerate an object it must be proportional to both its mass and its inertia

what are the three things said about acceleration…

Acceleration in directly proportional to the net force acting on the object, bigger forces produce bigger accelerations. Acceleration is inversely proportional to the objects mass, the bigger the mass the more inertia it has and the more it resists changes in motion, therefore an increase in mass is a decrease in acceleration. Acceleration is in the same direction of the net force, both are vectors both have the same directions.

What is the Unit of force ?

1kgm/s/s also known as a newton

How much is one newton ?

The amount of force necessary to give a 1kg object an acceleration of 1m/s/s

Comparing the two equations f=ma and w=mg …

Both: Both are a force acting on mass and giving it an acceleration

Force: The f is any given force, and the w is the force of weight

Acceleration: The a refers to any given acceleration it is general, the g refers to the accceleration due to gravity in free fall

General Difference: F=ma is any force acting on any object and giving it any acceleration, W=mg is the force of weight acting on an object in free fall and giving it an acceleration due to gravity in freefall.

What are the types of Force mentioned …

Why not fly dragons to space, launch today

1. weight: The force of gravity acting on mass

2. Normal force: A force acting on two solid surfaces that is at right angles with both surfaces

3. Drag: A forcr excerted by an object that is going through it

4. Thrust: A force released by a jet engine when exhaust gass is released quickly and pushes back on the engine.

5. Spring force: A force made by an elastic object

6. Lift: An upwards force acting on an air foil

7. Friction: A force between solid surfaces that is parallel to those surfaces

8. Tension: A force transmitted by a tough spring, wire, etc

Free-body Diagram …

A tool that helps applied in newton second law of motion to a mocing object in the attempt to predict its motion

Define Net Force …

The sum of all forces acting on an object

What does the F in newton second law refer to (Net force) ?

Acceleration is not merely proportional to the force acting on an object but rather the net force

Equilibrium …

The condition on an object when the net force acting on it equals zero

An object can have force acting on it yet….

Have no acceleration, as lonmg as the forces add to zero

give two example of an object with forces actinf on it but zero acceleration….

A book at rest in a table: The normal force and the weight of the book are equal and in opposite directions, therefore equal to zero.

A sky diver that has reached TV: The skydivers weight is equal and in opposite directions with the air resistance, therefore equal to zero.