“Background Information” text from the Teacher’s Edition

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It is suggested that you read the Physics Talk and
Example Analysis sections in the student text for
this activity before proceeding in this section. It is
also suggested that you read the teacher background
and student text for Chapter 3, Activity 10,
“Energy in the Pole Vault.”
Work, the product force x distance, is expressed injoules. Work is equivalent to energy and, indeed, istransformed into kinetic energy and gravitational
potential energy in the vertical jump.
Research has shown that the location of the centerof mass within the jumper’s body varies onlyslightly for the body positions assumed during theprocess of the vertical jump.
The force which lifts and accelerates the body’scenter of mass during a vertical jump is provided bymuscles of the leg, ankles, and feet.
The method of analysis used for this activity assumes that the
muscular force is constant as the body rises from
“ready” to “launch” positions; this is not entirely
accurate—in a real jump, the force varies—but is a
reasonable approximation of reality.
Active-ating
the Physics InfoMall
While “hang time” is discussed on the InfoMall, it is
in the sense of how long a football stays in the air
during a punt, and not how long a basketball player
stays (or seems to stay) in the air.
Note that gravitational potential energy is
mentioned in this activity, a topic we will encounter
at the end of Chapter 3. And, like at the end of
Chapter 3, you are encouraged to browse the
textbooks. If you perform a search of the InfoMall
for Work, Potential Energy, or Kinetic Energy, you
will want to limit your search to only one or two
stores at a time, or use additional keywords to
restrict your search.
Should you desire additional problems for your
students to work on, consult the Problems Place.
For example, Progressive Problems in Physics has 16
problems on Work, and 25 on Energy.