The topics of the Goal 1

1. Physics
Part 1: Forces
Part 2: Motion
Part 3: Magnetism & Electricity

2. Physics
Part 1: Forces

3. WHAT IS FORCE?
• OBJECTIVE
• Analyze the resulting effect of balanced and
unbalanced forces on an object's motion in
terms of magnitude and direction

4. WHAT IS FORCE?
• ANTICIPATORY ACTIVITY
• Try to define the concept of force.

5. WHAT IS FORCE?
• A force is a push or pull that causes an object to move, stop, or
change direction
• In physics a force is anything that makes an
object accelerate
Example: Friction and gravity are two types of forces we encounter
everyday.

6. HOW IS A FORCE
VREECPTROERSSE rNepTrEeDse?n t forces
A vector is a physical quantity with direction and magnitude.
Vectors are represented with arrows. The length of the arrow is
the magnitude and its orientation or where it points is the
direction.
Examples of vectors are: FORCE and VELOCITY.
Note: If a quantity has only MAGNITUDE and NO DIRECTION,
is called SCALAR
Examples of scalar quantities are temperature, and time.

7. Skill Practice – Have student push a desk. Exerting a force on the desk causes it to move. Have
two students push the desk in the same direction.
When two people exert a force on the object, in the same direction, the total force is the SUM
of both forces exerted.
+ =

8. Skill Practice – Have one student push a desk one way and have another student push it the opposite way.
(preferably same force in each direction)
When two people exert a force on the object, in the opposite direction, the total
force is the DIFFERENCE of both forces exerted. If the force is the same, then
they can cancel out each other.
- = 0
Net Force: The overall force on an object
after all the forces are added together.

9. When there is a net force acting on an object, the force
is said to be unbalanced.
An unbalanced force can cause an object to start
moving, stop moving, or change direction. An
unbalanced force acting on an object will change the
object’s motion.
+ =
An unbalanced force will cause an object
to accelerate. The object will accelerate
in the direction of the GREATER force.

10. Equal forces acting on one object in
opposite directions are called
Balanced forces.
Balanced forces (equal) acting on an
object will not change the object’s
motion.
+ = 0
The net force is
zero

11. • Consider an example of a balanced force
- a person standing upon the ground.
• There are two forces acting upon the
person.
• The force of gravity exerts a downward
force.
• The force of the floor exerts an upward
force.
• Since these two forces are of equal
magnitude and in opposite directions,
they balance each other.
• The person is at equilibrium.
• There is no unbalanced force acting upon
the person and thus the person
maintains its state of motion.

13. CHECK FOR UNDERSTANDING
What makes an arrow fly through the air to its
target?
What makes a long jumper thud to a stop?
What will make a soccer ball change direction?
If two kids are playing tug of war but the center is
not moving they have ___________ force.
If one of the kids in the tug of war game pulls
harder than the other then you have an
____________ force.
Which force will cause change in motion –
balanced or unbalanced?

19. • Since these two forces are of equal
magnitude and in opposite directions,
they balance each other.
• The book is said to be at equilibrium.
• There is no unbalanced force acting
upon the book and thus the book
maintains its state of motion.
• When all the forces acting upon an
object balance each other, the object
will be at equilibrium;
• it will not accelerate.

21. Force
• Force Is measured in newton (N)
– A newton is equal to the force of gravity
exerted in an object that weights 100 grams
(about 1/5 of a pound).

22. Force
• WORKING WITH FORCE VECTORS:
– The net force is the vector sum of all the forces.
That is, the net force is the resultant of all the
forces; it is the result of adding all the forces
together as vectors.

23. Force VECTORS
*Forces acting in the same
direction. (Net force is the sum
of the forces).
*Forces acting in opposite
directions (balanced if the net
force is zero newton).

24. Combining forces
• Two men paddle their canoe on a river

25. Example #1
• Two tugboats are moving a barge.
Tugboat A exerts a force of 3000 newtons
on the barge. Tugboat B exerts a force of
5000 newtons in the same direction. What
is the combined force on the barge?
3000N Tugboat A
Barge
Tugboat B
5000N
8000N = Total Force

26. Example #2
• Now suppose that Tugboat A exerts a
force of 2000 newtons on the barge and
Tugboat B exerts a force of 4000 newtons
in the opposite direction. What is the
combined force on the barge?
2000N Tugboat A
Barge
Tugboat B
4000N
2000N = Total Force

27. Friction and gravity: two types of forces we encounter everyday.
Gravity – is the force that acts to pull objects
straight towards the center of the Earth.
– An objects speed increases as it falls.
• Free Fall – When the only force acting on a falling object is gravity,
the object is said to be in free fall.
Friction – is the force that one surface exerts on
another when the two rub against each other.
• Friction acts in a direction opposite to the object’s direction of
motion.
• Without friction an object would continue to move at a constant
speed forever.

28. Gravity
• An object in free fall accelerates as it falls.
• In free fall, gravity is the only force acting on the
object so it accelerates.
– The rate at which objects accelerate is 9.8m/s/s.
– This means that for every second an object is falling,
its velocity increases by 9.8m/s.
• ALL objects in free fall accelerate at the same
rate.

29. • Despite the fact that all objects are
supposed to fall at the same rate, we
know that this is not always the case.
• For example, let’s think about the following
example:
– An maple leaf and an acorn falling.
Do they fall at the same
speed?
What causes the speed
to be different?

30. Friction
• The type of friction shown in the previous
example is air resistance.
• The greater the surface area of an object,
the greater the air resistance.
• Friction causes objects to slow down or
stop.

31. Gravity
pulling the
acorn down. Air resistance
working
against
gravity is
greater for
the leaf.
Air resistance
working
against the
acorn is less
than the leaf Gravity
pulling the
leaf down.
In this situation, the acorn
falls faster because it has
less surface area and
therefore, less air
resistance.

32. Friction
• Friction is increased by the amount of
surface area the object has in contact with
the surface.
– For example, tires with more surface area
have better traction on the road.
• Friction causes objects to slow down or
stop.

33. How is Force Calculated?
f = m x a (Newton’s second law of motion)
 Force ( f ) is anything that
makes an object accelerate
 mass ( m ) is a measure for
the amount of matter in an
object
 Acceleration is the rate of
change in velocity
BEWARE: velocity is different to speed!!!
*Velocity is a vector that has as magnitude
(the speed - how fast) and as
orientation the direction (+ or -)

34. Newton’s 1st Law (Also called the law of inertia)
• Greeks thought that the
natural state of an
object was at rest.
– ex. A ball stops rolling
– without friction an
object would never stop!
• Newton’s 1st an
object in motion tends
to stay in motion; an
object at rest tends to
stay at rest

35. Newton’s 1st Law (Also called the law of inertia)
• Inertia property of matter that resists a change
in motion
– An object with great mass has high inertia

36. Newton’s 2nd Law (f = m x a )
 2nd Law states that if a net force
acts on an object, it will cause an
acceleration of that object.
Force = mass x acceleration
 An object will only accelerate
if there is an unbalanced
force.
 An object in motion will
remain in motion without
changing its speed or
direction until an unbalanced
force acts on the object.

37. Newton’s 2nd Law (f = m x a )
FA = 1000 kg x 0.05 m/s/s
FA =
FB = 2000 kg x 0.05 m/s/s
FB =

38. Newton’s 2nd Law (f = m x a )

39. Newton’s 3rd Law (Action and reaction)
• 3rd Law states that for
every action there is an
equal and opposite
reaction
– If an object exerts a
force in a second
object, the second
exerts an equal and
oppositely directed
force in the first one

40. Newton’s 3rd Law (ACtion and reaction)
• For every action
there is an equal
and opposite
reaction
– A bird pushes down
on the air and the air
pushes up on the
bird

41. Newton’s 3rd Law

42. Newton’s Laws
• 1st Law: (inertia: objects tend to do what they are doing)
– cannon ball will rest until a force is put on it
– ball will roll straight until ramp puts a force on it
• 2nd Law: (f = m x a) force equals mass times acceleration
– greater force put on ball accelerates it more
– greater mass of ball but greater force on water
• 3rd Law: (every action has an equal but opposite reaction)
– ball moves right, cannon recoils left
– ball move down, water splashes up

43. Newton’s Laws
Check the following examples to understand how Newton's first
law occurs in everyday events:
a) car suddenly stops and you strain against the seat belt
b) when riding a horse, the horse suddenly stops and you fly
over its head
c) the magician pulls the tablecloth out from under a table full of
dishes
d) the difficulty of pushing a dead car
e) lawn bowling on a cut and rolled lawn verses an uncut lawn
f) car turns left and you appear to slide to the right
Demo: coin falls if force removed

44. Newton’s Laws
Check the following examples to understand how Newton's
second law occurs in everyday events:
a) hitting a baseball, the harder the hit, the faster the ball goes
b) accelerating or decelerating a car
c) The positioning of football players - massive players on the
line with lighter (faster to accelerate) players in the backfield
d) a loaded versus an unloaded truck
Demo: spring scale and
acceleration

45. Newton’s Laws
Check the following examples to understand how Newton's third
law occurs in everyday events:
a) rockets leaving earth--many physicists of the nineteen
hundreds (Goddard's time) said that rockets could never leave
the earth. How a spaceship flies in space?
b) guns being fired- Why they kick in proportion to the size of the
bullet.
c) two cars hit head on
d) astronauts in space
e) pool or billiards
f) jumping out of a boat onto the dock
g) sprinklers rotating
Demo: rocket balloon

46. Physics
Part 2: Motion

47. Position, Speed and Velocity
• Space and Position
• Graphs of Speed and Velocity
• Working with Equations

48. Objectives
• Calculate time, distance, or speed when given two of
the three values.
• Solve an equation for any of its variables.
• Draw and interpret graphs of experimental data,
including velocity versus position, and speed versus
time.

49. Position, Speed, and Velocity
Key Question:
How are position, speed, and velocity related?

50. Space and position
• In physics, the word position refers to the location of
an object at one instant.
• A position is always specified relative to an origin.
• The net change in position relative to the origin is
called displacement.

51. Position and distance
• Distance is a scalar quantity that refers to "how much ground
an object has covered" during its motion.
• Displacement is a vector quantity that refers to "how far out
of place an object is"; it is the object's overall change in
position.

52. Speed and distance
• Speed is the rate at which distance changes.
• In physics, the word rate means the ratio of
how much something changes divided by how
long the change takes.
• Constant speed means the same change in
distance is traveled every second.
• Speed is a scalar quantity that refers to "how
fast an object is moving."

53. Calculating speed
• The change in position is a
distance traveled in a given
amount of time.
• To calculate the speed of
an object, you need to
know two things:
– the distance traveled by the
object
– the time it took to travel the
distance

54. Calculating speed
• Since speed is a ratio of distance over time, the
units for speed are a ratio of distance units over
time units.