Download Motion

Motion
Motion
 Motion
is a change in position
Frame of Reference
A
place or object that is fixed (not
moving)
 Ex:


A bus is driving by.
Your reference is trees on the other side of
the bus. This shows the bus is moving
relative to the trees.
If you are in the bus and your reference is
the other kids on the bus the kids do not
appear to be moving.
Speed
 How
fast something is going
 Speed=Distance/Time
 Ex:
If I walk 6m and it takes 3s, what is my
speed?



Speed=Distance/Time
Speed=6m/3s
Speed=2m/s
Constant Speed
A
moving object that does not chnge its
speed
 On a distance time graph this would be a
strait line.
Average Speed
 Total
Distance/Total Time
 Average speed is important because
most cars do not move at a constant
speed during its entire ride.
Velocity
 Speed
 Ex:
in a particular direction
A car with a speed of 10m/s and
heading north would have a velocity of
10m/s northwards
Velocity Cont.
 Velocity
is a vector represented by an
arrow. The length of the arrow represents
speed and the way the arrow points
represents direction
Acceleration
 Change
in speed and/or direction
 Acceleration = Velocity/Time
 Speeding up=Positive acceleration
 Slowing Down=Negative acceleration
 Ex:
When a car slows down you move
forward, and when a car speeds up you
are pushed back into the seat.
Acceleration Cont.
Newton’s First Law
 An
object at rest tends to stay at rest and
an object in motion tends to stay in
motion with the same speed and in the
same direction unless acted upon by an
unbalanced force.
Newton’s First Law
 Also
called law of inertia
 Inertia is the tendency of an object to
resist change in its motion.
 Ex: When you break in a car suddenly.
Your body keeps moving forward
because of inertia.
 https://www.youtube.com/watch?v=yZM
EUT-Ipv4
Balanced/Unbalanced Forces
 Balanced
Forces – 2 forces are acting
in opposite directions with the same
amount of force. The net force would
be 0 and this object would not move.
 Unbalanced forces – 2 forces are
acting in the same direction, or in
opposite directions with different
amounts of force. The net force would
not be 0, and this object would move
in the direction of the larger force.
Net Force
 The
end result of the forces added
together (when acting upon an object in
the same direction) or subtracted from
one another (when acting upon an
object in opposite directions)
 If net force = 0 the object is not moving
 If net force ≠ 0 the object will move in
direction of larger force
Newton’s First Law
 Let’s
think about a book on a table.
 Once force acting upon the book is
gravity pulling it toward the ground
 A second force is the table pushing back
on the book.
 These forces are acting in opposite
directions with the same force so the
book is balanced or not moving
Newton’s First Law Cont.
 When
a book is being slid across the table
there are 4 forces acting upon the book.
 The table and gravity are equal so the
book does not move up or down.
 The push of the book acts in one direction
and friction acts in the opposite direction
 The push is a bigger force, so it causes the
book to move because that force is
bigger than the friction working against it.
Newton’s First Law Cont.
 Newton’s
1st law is sometimes called the
law of inertia
 Inertia – the tendency of all objects to
resist any change in motion
 Objects with smaller mass have smaller
inertia. This is why it is easier to push and
stop a bike than a car.
Newton’s Second Law of
Motion
 The
acceleration of an object depends
on the mass of the object and the
amount of force applied.
 Greater force = More acceleration
 Greater mass = Less acceleration
 All objects fall to the ground with the
same acceleration (9.8 m/s²)
Newton’s Third Law
 Whenever
one object exerts a force on a
second object, the second object exerts
an equal and opposite force on the first.
 https://www.youtube.com/watch?v=mFN
e_pFZrsA
 Ex: You sitting on a chair. The force of
gravity pulling you down is equal to the
force of the chair pushing up on you.
 Ex: dropping a ball. The force of gravity is
pulling the ball toward the ground and
the ground toward the ball
Newton’s third Law Cont.
 Unbalanced
forces result in movement
because the action and reaction act on
2 different objects.
 Ex:


Kangaroo Jumping
Action: Kangaroo on ground, Reaction:
ground on Kangaroo
Results in the kangaroo jumping
Law of conservation of Energy
 https://www.youtube.com/watch?v=8GLt
FNaiMH8