Los Altos High School
Physics Honors
Chapter 6 - Work and Energy
Work Energy Theorem
Conservation of Energy
Energy before  Energy nc  Energy after
WNet  KE
 
W  F  S  FSCos FS
KE 
1
mv 2
2
PE  mgh
Mr. Randall
Spring Semester 05-06
www.LAPhysics.com
[email protected]
Chapter 6 - Work and Energy
Assignments
Due Dates
1. #'s 3, 5, 7, 9, 10, 12
2. #'s 13, 14, 15, 22, 23, 25
3. #'s 27, 31, 33, 34 + (W+B)k #’s 1, 2, 3
4. #'s 35, 36, 37, 39, 42, 43, 44, 47
5. #'s 48. 50. 55. 57. 58 + (W+B)k #’s 4,5,6
6. #'s 59, 61, 73, 77, 82, 84, 85 + (W+B)k # 7
Quiz - 12/1/06 & 12/8/06
Unit Test – 12/15/06
Reading


All of chapter 6
Solve the example problems within each section.
Los Altos Physics Honors
0.
Consider a 85.0 kg clown sitting at the top of a frictionless slide, 22.0 m above the
ground. The bottom of the slide makes a slight circular turn and extends
horizontally 6.0 m. The lower end of the slide is 10.0 m above the ground. Calculate
the range of the clown as measured from the lower edge of the slide.
ho = 22.0 m
hf = 10.0 m
ΔX
1.
Consider two circus performers connected by a massless cord passing over two
frictionless pulleys. Performer 1 (30 kg) hangs, ready to swing like a pendulum,
suspended 12 m below the fulcrum. Performer 2 (60 kg) sits at rest on a spring scale.
A.
Sketch a graph of Performer 2’s apparent weight as a function of time (n vs. t) as
Performer 1 pendulum swings through small angles.
B.
Predict the height and angle (hc, c) at which Performer 1 swings from such that
Performer 2 achieves weightlessness.
r
c
Force Scale
h
2.
Consider a 65 kg circus performer at rest, 28.0 m above the ground. The only path
to the ground is a frictionless curved ramp. Predict the circus performer’s range
once it becomes a freefalling projectile.  = 25.
28 m

3.0m
3.
Consider a 65 kg circus performer performing the vertical loop trick. sliding from
rest down a frictionless track, the performer centripetally accelerates around a
vertical circle, r = 4.5 m.
A.
Predict the minimum height
the performer must start at to
safely make the loop?
B.
Is the ratio of the speed
at the top of the loop to the
speed at the bottom of the
loop is equal to:
Vtop
VBottom

5
?
5
ho
r
4.
Consider a 65 kg circus performer 28.0 m above the ground. The only path to the
ground is a rough curved ramp. During the slide down the ramp 7.6 kJ of energy is
lost due to work done by friction, a non-conservative force. Calculate the circus
performer’s range once it becomes a freefalling projectile.  = 25.
28 m

3m
5.
Consider a 65 kg circus performer performing the vertical loop trick. sliding from
2
rest down a rough k =
“linear” track inclined at  = 45 the performer
2
centripetally accelerates around a vertical circle, r = 4.5 m.
A.
Predict the minimum height
the performer must start at to
safely make the loop?
B.
Is the ratio of the speed
at the top of the loop to the
ho
speed at the bottom of the
Vtop
2

loop is equal to:
 5   ?
VBottom
r

r

6.
Consider a circus performer sliding down a frictionless incline, continuing across a
rough horizontal floor then grabbing onto a cable and pendulum swinging through an
exact right angle, 90.
A.
Predict the length of the horizontal slide from the bottom of the incline to the
hanging cable.
ho = 25 m
k=0
r = 10 m
37 = 
 k = 0.3
X = ?
7.
Consider the launching mechanism of a toy gun consisting of an ideal spring. When the spring
is compressed 0.120 m, the gun is able to launch a 0.035 kg projectile to a maximum height
of 20.0 m when released vertically from rest. Neglect the effects of friction:
A.
Predict the spring constant.
B.
Predict the speed of the projectile as it moves through the equilibrium position of the
spring.
8.
Consider a gallon of chocolate milk with a mass of 0.80 kg sliding across a horizontal
surface. The milk has an initial velocity of 1.2 m/s to the right just before it collides with an
ideal spring, k = 50.0 N/m.
A.
Predict the maximum compression of the spring during the collision.