Force and Motion: Stop Faking It!
The first of two Web Seminars on the topic of Force and Motion was held on Tuesday, December 5,
2006, from 6:30 p.m. to 8:00 p.m. Eastern time. The presenter was Dr. Bill Robertson, author of the
popular NSTA Press series of books: Stop Faking It! The presentation focused on the topic of gravity, a topic discussed on Dr.
Robertson's book: Force and Motion: Stop Faking It!
Seventy-four (74) participants were present in addition to the presenter and the
NSTA staff. Participating educators represented the states of Arkansas, California,
Florida, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maryland,
Massachusetts, Michigan, Missouri, Nebraska, Nevada, New Jersey, New York, North
Carolina, Ohio, Pennsylvania, Puerto Rico, Rhode Island, South Carolina, South Dakota,
Tennessee, Texas, Virginia, Washington, and Wisconsin. Some of the participants
had attended one of the two symposia on the same topic at the Area Conferences in
Omaha and Baltimore.
In this presentation educators had the opportunity to learn about the concept of
gravity. Dr. Robertson first talked about the effects of gravity on objects falling
close to the surface of the Earth. Robertson concluded that if you ignore air resistance,
all objects dropped from the same height land at the same time regardless of their
mass. Objects falling to the Earth have the same acceleration; this acceleration
is called "g" and it is equal to 9.8 meters per second per second. The presenter
then proceeded to define the term "weight." He described weight as the force of
gravity exerted by the Earth on all objects.
Dr. Robertson also explained how the force of gravity affects objects far away from
the surface of the Earth. He explained that a different mathematical expression
must be used to calculate the force of gravity exerted by the Earth on objects away
from the Earth's surface. To gain a better understanding of this concept, web seminar
participants used a simulation to manipulate the distance a satellite is located
from the Earth to determine its weight, i.e., the force of gravity exerted by the
Earth on it. The results showed that as an object moves away from the Earth, the
force of gravity exerted by the Earth on the object gets smaller. Dr. Robertson
concluded the web seminar talking about objects in orbit around the Earth or free
fall and the concept of weightlessness. All participants received a copy of NSTA's SciGuide on Force and Motion.
Here are some comments provided by the participants at the end of the Web Seminar:
- "It cleared up some misconceptions I had about acceleration and mass close to
- "My children love to do science; they are in the 5th grade. I was a secondary
science teacher before becoming a science teacher educator. I suspected that Bill
would have a better way to explain the concept to my kids and I was correct. Excellent
- "I teach pre-service teachers who really struggle with force and motion concepts.
Their intuitive ideas seem to block a more scientifically accurate explanation.
This was very relevant to my class needs."
- "There is always a lot of confusion between mass, weight, and gravity. The graphics
and question quizzes along the way helped a lot!"
Thanks to the participants and the presenter for the learning opportunity, the interactions,
and a job well done!
For more information contact firstname.lastname@example.org
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Underwritten in part by NSTA Press