Forces Acting On Objects

Moving and Stopping Mechanisms

Newtons

f= ma

9.8meters/Sec2

w= mg

Kinetic Friction

Nature of MassMass is a Fundamental Property of Matter

1,000 Cubic Centimeters of Water 1 Kilogram

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.

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 Second2

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 is a Force measured in Newtons Magnitude: Relative to the MassDirection: Center of the Earth

Weight = Mass x Acceleration of Gravity

9.8 (Newtons) =1 (kg) 9.8(Meters/Sec2)

W(Newtons) = m (kg) g(Meters/Sec2)

(W) Weight = 5 kg or 49 Newtons

fsF

W= mg

M1

Spring Scale

Weight is a Force Caused by Gravity Acting on the

Mass of an Object

49 Newtons = 5kg x 9.8m/s/s

Weight = Mass x Gravity

N

Stamp Issued by Germany on Jan. 14, 1993, on his 350th birthday

Image Courtesy of University of St.Andrews, Turnbull Server

Newton Provided Insights Into the Nature of Forces

Let’s Look at a Pair of Balanced Forces Acting on a Robot Resting on the Floor

Because the Floor Pushes Up with the

SAME Force

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

Newton’s 1st Law An object with no net force acting on it moves

with constant velocity. Force: 20 NewtonsForce: 20 Newtons

Same Force in Opposite Directions

There is no NET force on the system and the machines remain stationary

Velocity = 0

Newton’s 2nd Law

The acceleration of a body is directly proportional to the net force acting on it and

inversely proportional to its mass.

Robot Mass = 5 Kilograms

Acceleration = 4 meters/sec2

Tractive Force = 20 Newtons

Force = Mass x Acceleration20N = 5kg x 4m/s2

Build Newton’s Cart using the GEARS-IDS components and

experiment with Newton’s second law

f force= m mass a acceleration

Newton’s 2cd Law

Pulley

Newton’s Cart

Mass

Force Experiment with masses and forces, and their affect on acceleration

Using Newton’s Cart1.) Set the System Up on a High Flat Table

Pulley

Cart 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

Note: Separate the Cart and Pulley by 2x Table Height

5.) Allow the Weight to Drop and Time the Speed of the Cart Over a Known Distance

Calculate the Acceleration of the Cart

TT

DCa 2

Where:

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.

The rotating wheels push against the floor and propel the robot forward and

the floor backwards

Floor Momentum = mass x velocityFloor Momentum = 15 kg x 5 mps = 75

Robot Momentum = mass x velocity Robot Momentum = 5 kg x 15 mps = 75

Floor Board Rests on Frictionless

Bearing

The End