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Kinetic Friction
9.8meters/Sec2
Forces Acting On
w= mg Objects
Moving and Stopping Mechanisms
f= ma
Nature of Mass
Mass is a Fundamental Property of Matter
1,000 Cubic
Centimeters of Water
=
1 Kilogram
Mass
Gravity is force that
causes all objects
(matter) to accelerate
towards each other
At a constant rate and
with a force proportional
to their Mass
View of Africa and Saudi Arabia from Apollo 17. Probably the most requested picture
of the Earth, this picture was taken by the Apollo 17 astronauts as they left earth orbit
en route to the Moon. Taken on Dec. 7, 1972, it was the first time that the trajectory
of an Apollo mission enabled a view of the south pole.
Objects on the Earth’s
Surface accelerate
down at a rate =
9.8 Meters per
2
Second
View of Africa and Saudi Arabia from Apollo 17. Probably the most requested picture
of the Earth, this picture was taken by the Apollo 17 astronauts as they left earth orbit
en route to the Moon. Taken on Dec. 7, 1972, it was the first time that the trajectory
of an Apollo mission enabled a view of the south pole.
All Objects (Matter) Exert a
Gravitational Force On One Another
Proportional to Their Mass
Gravity is the Weakest
of the 4 Natural
Forces
Weight
Gravity’s Effect on Mass
Weight = Mass x Acceleration of Gravity
W(Newtons) = m (kg) g(Meters/Sec )
2
9.8 (Newtons) =1 (kg) 9.8(Meters/Sec )
2
Weight is a Force measured in Newtons
Magnitude: Relative to the Mass
Direction: Center of the Earth
Weight is a Force Caused
by Gravity Acting on the
Mass of an Object
N
F
fs
M1
Spring Scale
W= mg
(W) Weight = 5 kg or 49 Newtons
Weight = Mass x Gravity
49 Newtons = 5kg x 9.8m/s/s
Newton Provided Insights Into
the Nature of Forces
Stamp Issued by Germany on Jan. 14, 1993,
on his 350th birthday
Image Courtesy of University of St.Andrews, Turnbull Server
Let’s Look at a Pair of Balanced Forces
Acting on a Robot Resting on the Floor
The Force of Gravity
Acts to Accelerate This
Chassis Towards the
Earth’s Center
The Chassis is undergoing an
Acceleration, but it is Not
Moving
Because the
Floor Pushes
Up with the
SAME Force
Newton’s
st
1
Law
An object with no net force acting on it moves
with constant velocity.
Force: 20 Newtons
Force: 20 Newtons
Velocity = 0
Same Force in Opposite Directions
There is no NET force on the system and the
machines remain stationary
Newton’s
nd
2
Law
The acceleration of a body is directly
proportional to the net force acting on it and
inversely proportional to its mass.
Tractive Force = 20 Newtons
Acceleration = 4 meters/sec2
Robot Mass = 5 Kilograms
Force = Mass x Acceleration
20N = 5kg x 4m/s2
Newton’s 2cd Law
Build Newton’s Cart using the
GEARS-IDS components and
experiment with Newton’s
second law
Force
Mass
Experiment with
masses and forces, and
their affect on acceleration
Using Newton’s Cart
1.) Set the System Up on a High
Flat Table
2.) Connect a Masons String
from the Cart Through the
Pulley
3.) Attach a Weight (Force) to the
end of the Pulley Side of the Line
4.) Place a Known Mass on the
Cart
5.) Allow the Weight to Drop and
Time the Speed of the Cart Over a
Known Distance
Note: Separate the Cart and Pulley by 2x
Table Height
Calculate the Acceleration of the Cart
Where:
D
Ca     2 T
T 
Ca= Acceleration of the Cart in meters/sec/sec
D = Distance Covered in meters
T = Time in seconds
Newton’s Third Law
When one object exerts a force on a second object, the
second exerts a force on the first that is equal in magnitude
but opposite in direction.
Floor Board Rests
on Frictionless
Bearing
Robot Momentum = mass x velocity
Robot Momentum = 5 kg x 15 mps = 75
Floor Momentum = mass x velocity
Floor Momentum = 15 kg x 5 mps = 75
The rotating wheels push against the
floor and propel the robot forward and
the floor backwards
The End