VELOCITY
• Velocity (v) is the rate at which an object
is changing position per unit of time with
a direction.
• Direction is: north, south, east, west,
right, left, up, down.
• Velocity changes when one or both of the
following change: 1) speed 2) direction
• Velocity is measured in m/s or km/hr plus
direction. v = d/t + direction
• d = distance t= time
• Reference point is something that a
moving object’s position is compared to.
VELOCITY
Questions
1.What is the velocity of a car determined by?
2.When a vehicle starts moving at a faster rate,
what happens to the velocity of the vehicle?
3.Traveling down a straight highway, a car
changed velocity while its speed remained
constant. What most likely caused this to
happen?
VELOCITY
Questions
4. In which example can velocity be
determined?
A. A truck drives 50 km/hr
B. A boat sails southeast at 20km/hr
C. A train travels northwest for 30 km
D. A plane flies 80 km
VELOCITY
Answers
1. Speed and direction
2. The velocity changes because the
speed changed
3. The car changed direction
4. B. A boat sails southeast at
20km/hr
BALANCED & UNBALANCED FORCES
• Balanced forces are equal forces acting on an
object from different directions that keep the
object stationary (not moving).
• Forces have magnitude (size) and direction
(arrow).
• Forces are measured in Newtons.
• The Newton is a unit that measures force and
weight in the metric system
BALANCED & UNBALANCED FORCES
• 1. The arrows in the diagrams show the forces applied to
a stationary orange. In which diagram will the orange
remain stationary?
•
A
B
C
D
BALANCED & UNBALANCED FORCES
2. The picture shows the forces acting on a ball.
In which of the pictures will the ball remain
motionless?
A
B
C
D
BALANCED & UNBALANCED FORCES
3. Forces applied to a box below are indicated with arrows.
In which of the diagrams the box is in motion (moving)?
A
B
C
D
FORCE—GRAVITY
• Force is a push or a pull
• Force is measured in Newtons (N)
• Force has magnitude (a number) and
direction (arrow)
FORCE—GRAVITY
1. The picture shows a snail traveling up a hill.
Which arrow in the diagram represents the
force of gravity acting on the snail?
FORCES—FRICTION
• Friction is a type of force that opposes
motion. This means that friction goes against
motion and slows down the moving object. If
a surface is rough, there is more friction.
• If the surface is smooth, there is less friction
and you move faster.
• When an object is stationary (motionless) on a
surface, the surface is exerting an upward
force which is equal to the force of gravity.
• This results in balanced forces so the object
does not move or fall.
FORCES—FRICTION
Example: A vase on a table
• The table exerts a force of friction that is upward and
equal to the force of gravity.
• The vase does not fall.
• If you put a vase on a sheet of paper, it will fall because
the force of gravity is stronger than the friction exerted
by the paper.
gravity
• This results in unbalanced forces
and the vase falls.
friction
AIR RESISTANCE
• AIR RESISTANCE is a force exerted by air
paper
air resistance
FORCE
1. Force is a push or a pull. Force has direction.
When you ride your bike, a forward force is
applied on the pedal. Other forces act in the
opposite direction of the bicycle’s forward
motion. Which of the following combination of
forces act in the opposite direction?
A friction and gravity
B air resistance and gravity
C air resistance and friction
D gravity, air resistance, and friction
FORCE
Answer
C -- air resistance and friction
FORCE
2. A rock is resting motionless on a hill. What is
creating the force that is acting in the direction
of the arrow?
A gravity
B friction
C the hill
D the rock
FORCE
Answer
C-- The hill
FORCE
3. Devon placed a cup of soda at the top of an inclined
wooden board. The cup remained where he placed it.
Why did the cup stay at the top of the board?
A. The mass of the cup of soda was reduced by the force of
friction.
B. The force of friction equaled the force pulling the cup of
soda down the board.
C. The board decreased the amount of gravity acting on the
cup of soda.
D. The force of friction was greater
than the force pulling the cup of soda
down the board.
FORCE
Answer #3
B --The force of friction equaled the force
pulling the cup of soda down the board.
FORCE
4. If you release a block of wood and a block of ice
at the same time from the top of a slide, the ice
block reaches the bottom of the slide first. Why
did the wood reach the bottom last?
A. There was more friction on the wood
B. There was less friction on the wood
C. The force of gravity was stronger on the wood
than on the ice.
D. The force of gravity was stronger on the ice than
on the wood.
FORCE
Answer #4
A. There was more friction on the wood.
FORCE
5. The glass resting on a table is stationary.
Why?
FORCE
Answer #5
The table is exerting an upward force that
opposes gravity.
CENTRIPETAL FORCE
• Centripetal force is the force that pushes a
moving body toward the centre or
• a force which keeps a body moving with a
uniform speed along a circular path and is
directed towards the centre.
QUESTIONS
1. A car is traveling around a corner at a constant
speed.
Which diagram shows the direction of the
centripetal force that results in the change of
velocity?
CENTRIPETAL FORCE
CENTRIPETAL FORCE
Answer #1
C
BUOYANT FORCE
• Buoyant Force has an upward direction and a
magnitude equal to the weight of the water
(or liquid) displaced by a floating object.
Example: a cork or a boat floating in the water
is pushed upward by a force called buoyant
force that is equal to the weight of the water
that the boat or the cork is displacing.
BUOYANT FORCE
1. What is the direction and size of the buoyant
force acting on a boat or a cork floating in
water?
BUOYANT FORCE
Answer #1
Upward and equal to the weight of the water
displaced by the boat/cork.
BUOYANT FORCE
2. The arrows in the picture show the direction
and magnitude of four forces acting on a boat.
What determines the magnitude of the force
shown by arrow X?
A. The total volume of the boat
B. The size of the lake
C. The weight of the water displaced by the boat
D. The total mass of the person in the canoe
BUOYANT FORCE
BUOYANT FORCE
Answer #2
C. The weight of the water displaced by the boat