Science

1. Section 1 Gravity and Motion
Section 2 Newton’s Laws of Motion
Section 3 Momentum

2. • Gravity and
Acceleration
Objects fall to the
ground at the same
rate because the
acceleration due to
gravity is the same
for all objects.
• Acceleration Due to
Gravity
The object’s downward
velocity increases by
9.8 m/s.
Gravity and Falling Objects
Iron ball
Wood ball

3. Acceleration of
gravity is
independent of
the mass of the
falling object!

4. • Velocity of Falling Objects
You can calculate the change in velocity with
the following equation:
¨ ∆v = g X t
• If an object starts at rest, this equation
yields the velocity of the object after a
certain time period.

6. • Air resistance is the force that opposes
the motion of objects through air.
• The amount of air resistance acting on an
object depends on the size, shape, and
speed of the object.
Air Resistance and Falling Objects

8. ¨ As the speed of a falling object increases,
air resistance increases.
¨ The upward force of air resistance continues
to increase until it is equal to the downward
force of gravity. The object then falls at a
constant velocity called the
terminal velocity.

9. ¨ An object is in free fall :
- When There Is No Air Resistance
- only if gravity is pulling it down and
no other forces are acting on it.
A vacuum is a place in which there is no
matter. Objects falling in a vacuum are in
free fall because there is no air resistance.

10. ¨ Astronauts float in orbiting spacecrafts
because of free fall.

11. ¨ Orbiting and Centripetal
Force
The unbalanced force that causes
objects to move in a circular
path is called a centripetal
force.
Gravity provides the centripetal
force that keeps objects in
orbit.
Too slow => Object falls
back down to Earth
Too fast => Object
escapes Earth’s gravity

12. ¨ Projectile motion is the curved path an object
follows when it is thrown or propelled near the
surface of the Earth.
¨ Projectile motion has two components that are
independent of each other;;
-­ horizontal velocity
-­ vertical velocity

14. 1.A body continues
at rest or in
uniform motion in a
straight line unless
acted upon by
some net force.
An astronaut floating in space will continue to float
forever in a straight line unless some external force
is accelerating him/her.

15. ¨ Friction between an object and the
surface it is moving over is an example of
an unbalanced force that stops
motion.

16. ¨ Inertia is the tendency of all objects
to resist any change in motion.
¨ Mass is a measure of inertia.
- Small mass has less inertia
- Large mass has greater
inertia
Newton’s first law is sometimes called
the law of inertia.

17. ¨ The acceleration of an object depends on
the mass of the object and the amount of
force applied
a = F/m ó F = m a

18. ¨ Part 1: Acceleration Depends on Mass
The acceleration of an object decreases as
its mass increases.
¨ Part 2: Acceleration Depends on Force
An object’s acceleration increases as the
force on the object increases.
¨ The acceleration of an object is always in
the same direction as the force applied.

21. ¨ Whenever one object exerts a force on a
second object, the second object exerts an
equal and opposite force on the first.
To every
action, there
is an equal
and opposite
reaction.
All forces act in pairs.

22. ¨ Force Pairs Do Not Act on the Same Object.
¨ When a force is exerted, there is always a
reaction force.
A force is always exerted by one object on
another object.

23. • The momentum of an object depends on the
object’s mass and velocity.
P = m x v

24. ¨ The law of conservation of momentum states;
- that any time objects collide, the
total amount of momentum stays the same.
- After two objects stick together, they
move as one object
- The combined objects have a
different velocity because momentum
is conserved and depends on mass
and velocity.
• So, when the mass changes, the
velocity must change, too.

26. Objects Bouncing Off Each Other
• When two objects bounce off each other,
momentum is transferred from one object
to the other.
• The transfer of momentum causes the
objects to move in different directions at
different speeds.

27. ¨ Because action and reaction forces are
equal and opposite,
momentum is neither gained or lost in
a collision