Los Altos High School
Physics
Chapter 6 - Work and Energy
Solutions
Mr. Randall
Spring Semester – 2010
www.LAPhysics.com
adam.randall@mvla.net
Los Altos Physics
Workbook Problems - Work and Energy
1.
Consider a Volkswagen van initially at rest & out of gas. A group of people get behind the
van and push on it’s rear bumper with a net force of 565N in the forward direction, for a
distance of 15.0 m. If the van’s mass is 1250 Kg:
A.
B.
C.
D.
Predict the net work done on the van.
Predict the final speed of the van after the 15.0 m of displacement.
Predict the van’s change in kinetic energy during the 15.0 m displacement.
Sketch a qualitative graph of the van’s net force vs. displacement and briefly describe
what the area bound by the net force and displacement represent.
∆X = 15.0m
Workbook Problems - Work and Energy
2.
A 3.00 kg crate slides down a ramp at a loading dock. The ramp is 1.00 m in length
o
and inclined at an angle of 30.0 . The crate starts from rest at the top ,
experiences a constant frictional force of magnitude 5.00 N, and continues to move
a short distance on the flat floor.
A.
Use the work energy theorem to predict the speed of the crate when it reaches the bottom of the
ramp.
B.
Sketch three energy diagrams for the box at points A, B and C.
C.
Use the law of conservation of mechanical energy to predict the speed of the crate when it
reaches the bottom of the ramp.
A
L
h
B
θ
C
Los Altos Physics
Workbook Problems - Work and Energy
3.
Consider a 55.0 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
5
?
loop is equal to:
5
hA
r
4.
Consider a circus performer, initially at rest, sliding down a frictionless incline, continuing
across a frictionless horizontal floor, then grabbing onto a cable and pendulum swinging
through an exact right angle, 90.° before stopping.
A.
Predict the initial height of the incline the circus performer starts at to complete the 90.°
swing.
r = 10. m
ho = ?
µk=0
µk=0
37° = θ
Los Altos Physics
Workbook Problems - Work and Energy
5.
Consider a 85.0 kg clown resting 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.
hA = 22.0 m
hB = 10.0 m
∆X