# Assignment 08

```PHYSICS 111: WRITTEN ASSIGNMENT 08
Due date:
Thursday 8th Nov. 2007 at 1000 (Sec 03)
Friday 9th Nov. 2007 at 1030 (Sec 01)
Friday 9th Nov. 2007 at 1130 (Sec 02)
For each of the following questions, work out the solution using the problem-solving method discussed in
class and described in detail in the Survival Guide. Clearly label your submission by printing your class,
name, section, and student number in the upper right-hand corner of each page. Please staple your written
assignment pages together before handing it in.
1
Chapter 8, problem 20.
2
Chapter 8, problem 30.
3
A thin rod of length L is oriented vertically, with its bottom end attached to the
floor by means of a frictionless hinge. The mass of the rod is negligible compared to a
mass M fixed to the top of the rod. The rod, starting from rest, tips over and rotates
downward. Derive an expression for the angular speed of the rod just as it hits the floor.
m
L
L
v
INITIAL CONFIGURATION
4
Chapter 8, problem 50.
5
Chapter 9, problem 4.
FINAL CONFIGURATION
PHYSICS 111: ONLINE ASSIGNMENT 08
Due date: Friday 9th November 2007 at 1200 (noon)
For each of the following questions, work out the solution and select the choice that matches your calculated answer
to the given number of significant figures. If your answer does not match any of the choices, look for an error in your
solution. Carefully indicate your choices on the Assignment Submission form on the Physics 111 website. Also
record your choices on this question sheet since the website form responses will not be saved.
1
Chapter 8, problem 16.
(A) 1.45 s (B) 1.87 s (C) 3.76s (D) 4.82 s (E) 5.22 s
2 Chapter 9, problem 2.
(A) 8.50&times;102 N.m (B) 1.70&times;103 N.m (C) 2.40&times;103 N.m (D) 3.22&times;103 N.m
(E) 4.80&times;103 N.m
3
Which one of the following statements is NOT true for a rotating CD undergoing
angular acceleration?
(A)
(B)
(C)
(D)
(E)
4.
The angular speed is the same at any point on the disk
The linear speed is the same at any point on the disk
The angular acceleration is perpendicular to the centripetal acceleration
It may have zero angular velocity
The angular acceleration is the same for any point on the disk
The torque τ1 is produced in a counter clockwise direction on a lever arm of length
L by a force of magnitude F. If the lever arm is increased in length by 20%, and the
direction of the torque is reversed, what is the relationship between the new torque,
τ2, and the original torque?
(A) τ 2 = 1.2τ 1
(E) τ 2 = −
5.
τ1
(B) τ 2 =
τ1
1.2
(C) τ 2 = −0.2τ 2 (D) τ 2 = −1.2τ 1
0.2
A fan undergoes a constant angular acceleration of +α from rest to a final angular
velocity +ω. If this takes t seconds, what is the tangential velocity vT of a point on
the fan at a distance r from the centre of rotation?
αt
t
(A) vT = rω 0 (B) vT = rαt (C) vT =
(D) vT =
r
rα
ω
⎛ ⎞
(E) vT = ⎜ 0 ⎟t
⎝ r ⎠
```