Download motion and newton`s laws combined

Motion
Frames of Reference



The object or point from which
movement is determined
Movement is relative to an
object that appears stationary
Earth is the most common
frame of reference
Motion

Motion is a change in
position relative to a frame
of reference
Distance and Displacement

Distance is how
far you travelled

Displacement is
how far you are
from the starting
point, plus a
direction.
Quick Quiz

The diagram below shows the position of a crosscountry skier at various times. At each of the indicated
times, the skier turns around and reverses the direction
of travel. In other words, the skier moves from A to B
to C to D. Use the diagram to determine the resulting
displacement and the distance traveled by the skier
during these three minutes.
Answer

The skier covers a distance of
(180 m + 140 m + 100 m) = 420 m and has a
displacement of 140 m.
Speed

Speed is the distance traveled
in a given amount of time
• Speed=distance
•
time

The units for speed:
• meters/second (m/sec)
• kilometers/hour (km/hr)

Speed that does not change
is constant speed
Practice Problem

A runner completes a 400-m race in 43.9s.
In a 100-m race, he finishes in 10.4 s. In
which race was his speed faster?
What is the
formula for
speed?
400m  43.9s = 9.1m/s
100m  10.4s = 9.6m/s  FASTEST
Distance v. Time

represents the
motion of an
object
 time is plotted
on the
horizontal axis
and distance is
plotted on the
vertical axis
 can be used to
compare the
speeds of
Average speed
Total distance divided by
the total time
 Formula:
 Total distance
total time

Velocity

Speed in a given direction
Acceleration
 The
change in velocity
 Acceleration is measured
in m/sec/sec or m/sec2
 Formula is:
3 ways to Accelerate
 Speed
Up- Positive Acceleration
 Slowing Down- Negative
Acceleration
 Change Direction
Acceleration Graph

Speed vs Time
Centripetal Acceleration
 Acceleration
directed
toward the center of
circular path
Momentum

Momentum is the quantity of motion of
a moving body, measured as a product
of its mass and velocity
 Inertia is a property of Matter. (Thanks
Bill)
 Inertia is an objects resistance to
change. (in motion or not in motion).
 The more mass an object has the
greater its inertia
Momentum
 Momentum is equal to
the mass of an object
times its velocity
 momentum= mass x
velocity
Conserving Momentum

The law of conservation of
momentum states that the
total momentum is NOT lost,
only transferred




1. The hulk coaster at Universal’s Islands of
Adventure shoots out of a tunnel going from 0 mps
to 80 mps in 4 seconds. What is its acceleration?
2. A race car is speeding down the Talladega
Raceway behind the pace car at 90 mph. When the
pace car drives off the track, the race car
accelerates to 210 mph in .01 hour. What is its
acceleration?
3. A runner in a 5K (5000m) race paces himself.
His time at the end of the race is 25 minutes.
What is his speed?
4. A jet plane has flown from Boston to New
York, a distance of 330 miles, in 15 minutes.
What was its speed?
Newton’s
Laws of Motion
I Law of Inertia
II F=MA
III Action-Reaction
Newton’s Laws of Motion
 1st Law – An
object at rest will stay
at rest, and an object in motion will
stay in motion at constant velocity,
unless acted upon by an unbalanced
force.
 2nd Law – Force equals mass times
acceleration.
 3rd Law – For every action there is
an equal and opposite reaction.
1st Law- Law of Inertia
 Inertia
is the
tendency of an
object to resist
changes in its
velocity:
whether in
motion or
motionless.
Partner
Why then, do we observe
every day objects in motion
slowing down and becoming
motionless seemingly without
an outside force?
Objects on
earth, unlike
the frictionless
space the moon
travels
through, are
under the
influence of
friction.
What is this unbalanced force that acts on an
object in motion?

There are four main types of friction:
• Sliding friction: ice skating
• Rolling friction: bowling
• Fluid friction (air or liquid): air or water
resistance
• Static friction: initial friction when moving an
object
Newtons’s 1st Law and You
Because of inertia, objects (including you)
resist changes in their motion. When the
car going 80 km/hour is stopped by the
brick wall, your body keeps moving at 80
m/hour.
1st Law and Net Force

Net force is the overall force (unbalanced) acting
on an object causing it to accelerate in a
direction.

In these scenarios which way will the block
move?
nd
2
Law
2nd Law


When mass is in kilograms and acceleration is
in m/s/s, the unit of force is in newtons (N).
One newton is equal to the force required to
accelerate one kilogram of mass at one
meter/second/second.
Newton’s 2nd Law proves that different masses
accelerate to the earth at the same rate, but
with different forces.
We know that
objects with
different masses
accelerate to the
ground at the
same rate.
 Earth’s Gravity
pulls all objects
towards Earth at
9.8m/s/s

rd
3
Law
 For every action, there is an
equal and opposite reaction.
The 3rd law
includes 2
forces acting
against each
other. These
two forces are
called action
and reaction
forces.
rd
3
Law
3rd Law
The reaction of a rocket is
an application of the third
law of motion. Various
fuels are burned in the
engine, producing hot
gases.
The hot gases push against
the inside tube of the rocket
and escape out the bottom
of the tube. As the gases
move downward, the rocket
moves in the opposite
direction.