Newton's laws of motion describe the relationship between an object and the forces acting upon it. According to Newton's first law, also known as the law of inertia, objects at rest will stay at rest and objects in motion will stay in motion with the same speed and direction unless acted upon by an unbalanced force. Newton's second law states that acceleration is produced when a force acts on an object, and greater force is required to accelerate objects with greater mass. Newton's third law describes action-reaction pairs, where every action has an equal and opposite reaction.

1. According to Newton's first law...
An object at rest will remain at rest
unless acted on by an unbalanced force.
An object in motion continues in motion
with the same speed and in the same
direction unless acted upon by an
unbalanced force.
This law is often called
"the law of inertia".

2. • What does this mean?
• This means that there is a natural tendency of
objects to keep on doing what they're doing. All
objects resist changes in their state of motion. In
the absence of an unbalanced force, an object in
motion will maintain this state of motion.

3. Let's study the "skater" to understand
this little better.

4. • What is the motion in this picture?
What is the unbalanced force in this picture?
What happened to the skater in this picture?

5. This law is the same reason why you should
always wear your seatbelt.

6. • According to Newton's second law...
• Acceleration is produced when a force acts on a
mass. The greater the mass (of the object being
accelerated) the greater the amount of force
needed (to accelerate the object).

7. • What does this mean?
• Everyone unconsciously knows the Second Law.
Everyone knows that heavier objects require more
force to move the same distance as lighter objects.

8. If this boy wants to accelerate the wall
in a forward direction, heavier mass
greater force required

9. Boy wants to kick the ball. Its easy to
move the lighter ball with little force
applied

10. • However, the Second Law gives us an exact
relationship between force, mass, and
acceleration. It can be expressed as a
mathematical equation:
Or
FORCE = MASS times ACCELERATION

11. Mike's car, which weighs 1,000 kg, is out of gas.
Mike is trying to push the car to a gas station,
and he makes the car go 0.05 m/s/s. Using
Newton's Second Law, you can compute how
much force Mike is applying to the car.

12. • Answer = 50 Newton

13. • For every action there is an equal and opposite re-
action.
• What does this mean?
This means that for every force there is a reaction
force that is equal in size, but opposite in direction.
That is to say that whenever an object pushes another
object it gets pushed back in the opposite direction
equally hard.

14. Let's study how a rocket works to understand
Newton's Third Law.
The rocket's action is to push down on the
ground with the force of its powerful engines,
and the reaction is that the ground pushes the
rocket upwards with an equal force.

16. • 1. Who was the scientist who gave us the Laws of Motion?
2. How many Laws of Motion are there?
3. What is another name for the first law of motion?
4. Which law explains why we need to wear seatbelts?
5. Which law says that force is equal to mass times
acceleration (F=MA)?
6. Which law says that heavier objects require more force
than lighter objects to move or accelerate them?
7. Which law explains how rockets are launched into space?
8. Which law says that for every action there is an equal and
opposite reaction?

17. Atomic physics
The branch of physics concerned with the
structure of the atom and the
characteristics of subatomic particles.
OR
The branch of physics concerned with the
structure and behavior of atomic nuclei.