Q9.1.a
Two pucks lie on ice and can slide with little friction. A string is attached to each
puck and the string is pulled with a constant force F. The string is wound around the
outer edge of puck 1 but attached to the center of puck 2. They both start from rest.
Try to imagine what you would see as they move. What do you think will happen in
the next 3 seconds?
F
1
1) 1 will move farther than 2
2) 2 will move farther than 1
3) 1 and 2 will move the same distance
2
F
Q9.1.b
Two pucks lie on ice and can slide with little friction. A string is attached to each
puck and the string is pulled with a constant force F. The string is wound around the
outer edge of puck 1 but attached to the center of puck 2. They both start from rest.
Apply the momentum principle to each puck. What does it predict should happen in
the next 3 seconds?
F
1
1) 1 will move farther than 2
2) 2 will move farther than 1
3) 1 and 2 will move the same distance
2
F
The VPython program referred to in the following questions (9.1a - 9.2a) is
09_Krel.py
Q9.1.a : Watch the objects move (VPython program)
Which object has the greater total
momentum (magnitude)?
1) Top object (blue)
2) Bottom object (red)
3) Their total momentum is the same
Q9.1.b : Watch the objects move (VPython program)
Which object has the greater total
kinetic energy?
1) Top object (blue)
2) Bottom object (red)
3) Their total kinetic energy
is the same
Q9.2.a : Watch the objects move (VPython program)
Which object has the greater
translational kinetic energy
(KTRANS)?
1) Top object (blue)
2) Bottom object (red)
3) Their translational kinetic energy
is the same
The VPython program referred to in the following questions is
09_RotateVibrateTranslate.py
Q9.2.b : Watch the object move (VPython program)
Ball on right (red) moving in +x
1) +x
direction, spring stretching, ball
2) –x
on left (magenta) at rest.
3) 0 (no direction)
⃗ 𝑪𝑴 ?
What is the direction of 𝒗
Q9.2.c: Watch the object move (VPython program)
Ball on right (red) moving in +x
1) +x
direction, spring stretching, ball
2) –x
on left (magenta) at rest.
3) 0 (no direction)
⃗ 𝑹𝑬𝑳 for
What is the direction of 𝒗
the left ball (magenta)?
Q9.2.d, 9.2.e, 9.2.f: Watch the object move (VPython program)
In the case shown in the
1) Ktrans
VPython program, what
2) (Kvib + Uspring)
energy terms are nonzero for 3) Krot
the system of the two balls
4) (Kvib + Uspring) and Krot
and the spring?
5) Ktrans and Krot
6) Ktrans and (Kvib + Uspring)
7) (Kvib + Uspring) and Krot and Ktrans
Q9.2.g, 9.2.h: Watch the object move (VPython program)
The system starts from rest.
1) Ktrans
A constant force is applied to 2) (Kvib + Uspring)
the right (red) ball, so
3) Krot
Wext > 0.
4) Ktrans + Krot
5) Ktrans and (Kvib + Uspring)
What energy terms increase? 6) (Kvib + Uspring) and Krot
7) (Kvib + Uspring) and Krot and Ktrans
Q9.3.a: A diatomic molecule such as molecular nitrogen (N2) consists of two atoms
each of mass M, whose nuclei are a distance d apart. What is the moment of inertia
of the molecule about its center of mass?
1) Md 2
2) 2Md 2
1
Md 2
2
1
4) Md 2
4
5) 4Md 2
3)
d
Q9.3.b: The spokes of a bicycle wheel have low mass, so almost all of the
mass of the wheel is concentrated in the rim. What is the moment of inertia
of a bicycle wheel of radius R and mass M?
1) MR2
2) 2  MR2
3) 2  RM
4) (1/2) MR2
5)  MR2
Q9.3.a
Two balls of mass 0.7 kg are connected by a low mass
rigid rod of length 0.4 m. The object rotates around a
pivot at its center, with angular speed 13 radians/s.
What is the rotational kinetic energy of this object?
1) 484 J
2) 4.73 J
3) 2.37 J
4) 0.056 J
5) 0 J
Q9.4.a Through what distance did the force act on the Point Particle system?
1) 0.03 m
2) 0.04 m
3) 0.07 m
4) 0.08 m 5) 0.10 m
Q9.4.b Through what distance did the force act on the Real system?
1) 0.03 m
2) 0.04 m
3) 0.07 m
4) 0.08 m 5) 0.10 m
Q9.4.c Which is the energy equation for the Point Particle system?
1) Ktrans = F*(0.07 m)
2) Ktrans = F*(0.08 m)
3) Ktrans + Kvib + Uspring = F*(0.07 m)
4) Ktrans + Kvib + Uspring = F*(0.08 m)
Q9.4.d
For the Point Particle system, what
was the total external work?
1) F*b + –mg*b
2) F*a + –mg*b
3) F*(a+b) + –mg*(b)
4) F*(a+b) + –mg*(a+b)
You pull up with constant force F
Q9.4.e
For the Real system, what
was the total external work?
1) F*b + –mg*b
2) F*a + –mg*b
3) F*(a+b) + –mg*(b)
4) F*(a+b) + –mg*(a+b)
You pull up with constant force F
Q 9.4.f: A skater pushes straight away from a wall. She pushes on the wall
with a force whose magnitude is F, so the wall pushes on her with a force F
(in the direction of her motion). As she moves away from the wall, her center
of mass moves a distance d. What is the correct form of the energy principle
for the real system consisting of the skater?
1) K trans  Einternal  Fd
2) K trans  Einternal   Fd
3) K trans  Einternal  0
4) K trans  Fd
5) K trans   Fd
Q9.4.g: A skater pushes straight away from a wall. She pushes on the wall with a
force whose magnitude is F, so the wall pushes on her with a force F (in the
direction of her motion). As she moves away from the wall, her center of mass
moves a distance d. What is the correct form of the energy principle for the point
particle system for the skater?
1) K trans  Einternal  Fd
2) K trans  Einternal   Fd
3) K trans  Einternal  0
4) K trans  Fd
5) K trans   Fd
Q9.4f
You pull on both ends of a spring. Each
hand exerts a constant force of 5 N. Each
hand moves a distance of 0.4 meters, so
the spring is stretched a total of 0.8
meters.
Consider the spring as a real system.
What is the change in the total energy of
the spring due to the work done by you?
1) 0 J
2) 2 J
3) 4 J
4) 5 J
Q9.4g
You pull on both ends of a spring. Each
hand exerts a constant force of 5 N. Each
hand moves a distance of 0.4 meters, so
the spring is stretched a total of 0.8
meters.
Consider the spring as a point particle.
Calculate the change in the translational
kinetic energy of the spring.
Ktrans =
1) 0 J
2) 2 J
3) 4 J
4) 5 J
Q9.4h
You pull on both ends of a spring. Each
hand exerts a constant force of 5 N. Each
hand moves a distance of 0.4 meters, so
the spring is stretched a total of 0.8
meters.
You did 4 J of work on the spring, but the
translational kinetic energy of the spring
did not change. What happened to the 4 J
of energy you expended?
1) The spring potential energy increased
2) The spring potential energy decreased
3) The 4 J was lost