1. Newton’s laws of motion
Dynamics
lesson 1

2. 1 - Inertia law
A body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.
A body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.
A body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.

3. 1 - Inertia law
If there is no unbalanced force:
The stones will fall anyway
The stones will remain steady
Why?
As the inertia law says, a body at rest will remain at rest unless an unbalanced force acts upon it. If there is no unbalanced force, nothing will be expected to happen.
As the inertia law says, a body at rest will remain at rest unless an unbalanced force acts upon it. If there is no unbalanced force, nothing will be expected to happen.

4. 1 - Inertia law
If the paper is pulled out quickly:
The coin will fall into the water
The coin will follow the paper
Why?
The force is acting on the paper so no change in motion is expected to happen to the coin. It will remain in the same place and then fall as nothing is supporting it.
The force is acting on the paper so no change in motion is expected to happen to the coin. It will remain in the same place and then fall as nothing is supporting it.

5. 2 - Fundamental law F ___ F = m·a a = m
The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.
The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.
The acceleration produced by a particular force acting on a body is directly proportional to the magnitude of the force and inversely proportional to the mass of the body.
a = F m
___
F = m·a
I.S. units Newtons (N)

6. 2 - Fundamental law
The apple falls in a way that:
Its speed is constant
It increases velocity steadily
Why?
As an unbalanced force is acting, a change in apple’s motion will happen. This change implies a change in its speed. This change is represented by an acceleration (gravity in this case).
As an unbalanced force is acting, a change in apple’s motion will happen. This change implies a change in its speed. This change is represented by an acceleration (gravity in this case).

7. 2 - Fundamental law
Who gets the highest acceleration?
The elephant
The boy
Both get the same
Why?
The force will be bigger for the elephant, but the acceleration will be the same for both!!!
The force will be bigger for the elephant, but the acceleration will be the same for both!!!
Be careful about that!!

8. 3 - Action - reaction law
To every action (Fa) there is always an opposed an equal reaction (Fr).
To every action (Fa) there is always an opposed an equal reaction (Fr).
To every action (Fa) there is always an opposed an equal reaction (Fr). Fr Fa Fa Fr
Action and reaction forces act upon different bodies
They can be cancelled!!
NOT

9. 3 - Action - reaction law Who is making the action force? The girl
The boy
Both of them
Why?
Actually both of them are performing an action force upon the other. However, two reaction forces appear as well.
Actually both of them are performing an action force upon the other. However, two reaction forces appear as well.
simulation

10. 3 - Action - reaction law To turn right the skier…
Presses the left ski upon the snow
Presses the right ski upon the snow
Why?
The skier performs the action force, but is the reaction force from the snow which will allow him to turn right.
The skier performs the action force, but is the reaction force from the snow which will allow him to turn right.
simulation