bkik

1. •
•
of forces
Force
Motion
on the• Effects
•
object's motion
Forces on objects at rest
• Normal force
• Friction
• Gravitational force
•
•
Scalar
Vector
quantity
quantity
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8. Key Words Balanced
force Unbalanced
force
Resultant or Net Force
Learning Objective
Aim high - Be able to represent forces using a force diagram
Aim higher - Describe the effect that balanced and unbalanced forces
have on an object
Aim even higher - Be able to calculate the size of the resultant force
:

9. • A force
move,
is a push or pu11 that
causes
an object to
stop, or change direction
• In physics
accelerate
a force is anything that makes an object
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10. •
•
Forces
Forces
come
have
in pairs
a magnitude and a direction
Magnitude: 5N
Direction: north
5N, north (up
) (up
)
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11. • Forces occur in pairs and they can be
either balanced or unbalanced
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12. • Balanced
motion
forces do not cause change in
• They are equal in size and opposite in
direction
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13. on the book
Oil thebook are balanced.The forces
PHYSIC
S
PH

14. We call this NORMAL FORCE. The book is
said to be at equilibrium since there are no
unbalanced forces acting
state
upon the book
and
sits
it maintains its of motion (it still
on the table).
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15. Gravitypdls
dOWIJllllf8.M
S on the
l)e:tSOll
The Oom
pushes
upwudonthe
pe:rs4•.
Lets say you are
standing on the
ground. Since
the floor
upward
pushes
on you
and gravity is
pulling down on
you, you are at
equilibrium.

16. • An unbalanced force always causes a change in
motion
• When unbalanced forces act in opposite
directions you can find the net force
- Net force
• Magnitude
- The
difference
between the two forces
• Direction
- Direction of the largest
force
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17. ', I I 'I
-
left =
3N,
3
N,
right
-
6
N,
left
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18. =
.......4
N,
left - 10
N,
right =
6N,
right
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19. ..... -
10 N, right=
+
5 N, right± 15N, right
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20. Balanced Forces
Forces are
strength
balanced if they are the same
directions:but in opposing
40N 40N

21. Balanced forces
•
-

22. Balanced forces
Upthr
ust
of
welter
-
Welgl:il of boat

23. Unbalanced Forces
When forces working in opposite directions
are unequal they are unbalanced:
•Which direction will the box move?
100N

24. c Unbalanced forces
Unbalanced forces
-------
Truck
speed
up in this
direction
Smaller
force
60N
Bigger
force
100
N

25. ormal
The forces are balanced/unbalancedThe forces are balanced/ unbalanced
The woman is moving/ not movingThe man is moving/ not moving
I
Thrust
The forces are balanced/ unbalanced
The car is moving/ not moving

26. ApplicationQuestions
1. A diver wears weights and dives into the
water, which force is bigger, his weight or
upthrust? Draw a diagram to show the
forces acting on him
2. The diver then releases the weight. Now,
orwhich force is bigger, his weight
upthrust? Draw a diagram to show the
forces acting on him.

27. Resultant Force
If two forces are unbalanced there is a
resultant force.
It could replace all the others to give the
same effect.
The difference between two forces is the
resultant force.

28. What is the resultantforce?
Hint: work out the difference
the two forces.
between
The resultan
t
force is 1
OON -
20N = 80N
100N

29. Resultant forces - question 1
1.A. What is the
resultant force on
the
B.
satellite?
To which
direction will the
satellite move?

30. sN
Resultant forces -
2.
a.
question2
What is the
I
i horizontal resultant
force on the bird?
b. What is the
resultantvertical
force?
c. To which direction
will the bird move?

31. 10N
Resultant forces - question3
13N
3
.
a.
What is the horizontal resultant force on the
yacht?
b.
c.
What is the vertical resultant force?
To which direction will the yacht move?

32. Resultant forces - question1
1. What is the resultant force on the satellite?
Resultant force = 20 N - 10 N
= 10N down
The satellite will accelerate
downwards.

33. Resultant forces - question2
2. What is the resultant force on the bird?
The forces acting in each
direction horizontally are equal
in size, so there is no resultant
force in this direction.
Resultant force= 5 N - 5 N = 0
N
I7
'
The vertical forces are not
balanced, the bird will accelerate
in a downwards direction.
Resultant force = 5N - O
N= 5N down

34. 10N
10N
Resultant forces - question3
3. What is the resultant force on the yacht?
13N
The vertical forces are equal in size and opposite in direction
so there is no resultant force in the vertical direction.
The horizontal forces are not balanced, so the yacht will
accelerate to the right.
= (20 N + 10 N) -
= 17N right
Resultant force 13 N