This preview shows pages 1–2. Sign up to view the full content.
Scott Pratt
 PHY231, Spring 2006  Introduct
1
Midterm 2 (lecture students)
4 pt
Two velcrocovered pucks slide across the ice, collide
and stick to one another.
Their interaction with the ice is
frictionless.
Puck A is moving to the right at 6 m/s.
Puck
B has twice the mass as the Frst puck and is also moving to
the right, but at a slower speed of 2 m/s.
.
Puck A will increase its speed after the collision.
1
.
A
±
True
B
±
False
.
Momentum is conserved in the collision.
2
.
A
±
True
B
±
False
.
Puck B will increase its speed after the collision.
3
.
A
±
True
B
±
False
.
Kinetic energy is conserved in the collision.
4
.
A
±
True
B
±
False
2 pt
M
M
a)
b)
M
c)
Consider the Fve identical springs shown above supporting
the three identical masses as shown.
When in equilibrium,
the energy stored in the spring in (a) is U
a
, the combined
energies stored in the two springs joined endtoend in (b) is
U
b
, and the combined energies stored in the two springs in
(c) is U
c
.
.
U
c
is
U
a
5
.
A
±
one fourth
B
±
one half
C
±
equal to
D
±
twice
E
±
4 times
.
U
b
is
U
a
6
.
A
±
one fourth
B
±
one half
C
±
equal to
D
±
twice
E
±
4 times
4 pt
A
B
C
D
E
F
G
H
J(out of page)
I(into page)
The race car above travels at constant speed around a circular
banked race track as shown. The designers chose a banking
angle such that at 150 mph, a car could travel around the
track even in slick conditions when frictional forces between
the tires and road would disappear. Vectors AJ have direc
tions shown in the picture, with vector J pointing out of the
page in the direction the car is moving and I pointing op
posite the car’s velocity. Vectors D and H are perpendicular
to the surface, while vectors B and ± are parallel to the sur
face.
Vectors A and E are horizontal, while vectors C and
G are vertical.
±or these questions, ignore the e²ects of air
resistance.
.
If the car is going at a constant speed of 100 mph, the
direction of the frictional force acting on the car (due to the
track) is described by vector
.
7
.
A
±
A
B
±
B
C
±
C
D
±
D
E
±
E
F
±
F
G
±
G
H
±
H
I
±
I
J
±
J
.
If the car is moving at a constant speed of 150 mph, the
direction of the net force acting on the driver is described by
vector
.
8
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 smith
 Friction

Click to edit the document details