Download Guided reading 2

GUIDED READING
Unit 5: Newtonian Mechanics – Energy
NOTE: Your textbook discusses conservative and nonconservative forces. This is an AP Physics C concept.
For our purposes, you can disregard the words “conservative” and “nonconservative.”
Reading 1: pages 171 and THEN 295-296 and THEN 164 (first yellow box and the short ¶ after it)
 Describe an object that has gravitational potential energy. Then generate a practice problem to
calculate the object’s gravitational potential energy. Complete the calculations, being sure to
include units.

A Joule is a Newton·meter, break it down to fundamental units (kg, m, and s) based on a
Newton’s fundamental units. (Remember that Force = mass x acceleration.)

Based on your previous answer, show how the formula for gravitational potential energy gives
you these units.

Describe an object that has elastic potential energy. Then generate a practice problem to
calculate the object’s elastic potential energy. Complete the calculations, being sure to include
units.
GUIDED READING

Describe an object that has kinetic energy. Then generate a practice problem to calculate the
object’s kinetic energy. Complete the calculations, being sure to include units.
Reading 2: pages 160-171 and 182(bottom) - 183
 What does work do? (Hint: If ____ doesn’t happen, then no work must have been done.)

Generate an example of positive work being done.

Generate an example of negative work being done.

Generate an example of a force resulting in zero work being done.

Explain how you could solve for work: Gravity pulls a wagon of mass, m, down a ramp of height,
h, and elevation θ, so that it rolls a particular distance down the hill, d.

Generate an example of a situation in which the force varies as the displacement increases. (In
other words, the force applied isn’t constant as the object moves.)
GUIDED READING

Your friend reads the definition of the work-energy theorem that is on the bottom of page 164
and doesn’t understand it. Explain it to him in plain English.

What would negative work do to an object’s kinetic energy?

Generate and solve a sample problem in which you find an object’s final velocity when a force
pushes it for a particular distance.

Generate and solve a problem in which you solve for the height of an object after a particular
force has lifted it a given distance from an initial height.
GUIDED READING


Examine the statement at the beginning of the first full paragraph on page 183 (after reading
the bottom of page 182.) Think about it until you understand it.
Generate your own example of a variable force doing work, and explain how you could
determine how much work the force does.
Reading 3: pages 171 (bottom) – 178 and 182
 How are conservative and nonconservative forces different?

Generate an example of a conservative force doing work.

Generate an example of a nonconservative force doing work.1

List all types of mechanical energy.

Rewrite the sentence in the yellow box on page 174 in your own words.
1
Note: What’s most important about conservative/nonconservative forces in our course is what’s in
the yellow box on page 174.
GUIDED READING

Generate a problem in which an elevated object that is already moving falls to a lower elevation.
Your problem should allow you to solve for either final height or final velocity, and Wnc = 0J.

Generate a problem in which Wnc does not equal zero. Solve for Wnc.
Reading 4: 179 – 181
 Try to answer the question in the purple box on page 179 without looking in the back of the
book.

A car moves along a road at a constant speed. How might power relate to the amount of
negative work done by friction and air resistance? (Key: “constant speed”)
GUIDED READING

Examine the formula at the bottom of page 181 (“Solution”). Generate a problem to calculate
the power required to maintain the motion of an object with a given constant acceleration.