**Errors in Jan 2009 version of Ruina/Pratap
**Help us improve the book (typo, math error or any other error): Send
us email: ruina@cornell.edu

Suggestions for improvement of *any* kind are MOST WELCOME.
For example, have you looked for something in the book and had trouble finding
it? Whether you eventually found it or not, we'd like to know. That is, we
want it to be easier for students or people using the book as a reference to
find what they need in the book. Or, is there something that you think could
be explained better? Give us some clues about your confusions.

**Make money** if you are the first to find an error: $1.00 for
math errors, $5 for real errors or things that really deeply need fixing (with
suggestion about how to fix). How?: Subject
line in email: TEXT ERRORS. Then list like this (or like the Known Errors below,
XX are your initials):

Sect 13.2, pg 642, paragraph above "More about pendula". -XX 2/5/09

In the argument of the exponentials change gt/l to +- sqrt(g/l)t.

**Known Errors** (updated 6/20/09)

We keep track of typos, case and tense mismatches, mising closing parentheses,
spelling and grammatical errors, etc, but don't list them here. The things
listed here are real technical errors. (**-**XX are initials of the discoverer,
date is date of posting here , * = source files already fixed).

All of the errors below, as well as a few hundred other typos of various kinds, will be corrected in the next printing.

**Errors in HW problems
***Prob 4.99, p245 -MC, 12/21/08:

Lines IA, JD and BH should all be drawn as bars (not light or dashed lines).

Prob 5.51c, page 306. -AR 1/19/09

Should find moment in AD (not BD).

Prob 6.1, page 351 and 997 -MC 1/19/09:

Answer in back should be 10N (not 1000N).

Prob 6.19, page 352 -MC 1/19/09:

Suitcase is uniform density.

Suitcase height should be marked as l/3 (thats ell).

Force should be applied at end of handle.

Prob 6.25, page 353, -ABR 3/22/09

The drawing is missing a link between the two dots on the cutter blades.

Prob 9.17, page 501-2 -MC 1/21/09

Change F_0 = 5N to F_0 - 5 N/s.

(Otherwise the units are wrong. Another fix would be to change t to t/s in the
eqn.)

Prob 9.84, page 509, first par of prob. -MC 2/7/09

Change vA+ = 8 m/s to
vA+ = 6 m/s.

(As printed, masses pass through each other in collision.)

Prob 9.69, page 507. -MC 2/9/09

Change "..., c1, and F, " to "...
and c1." (ie, get rid of F).

Prob 9.91, page 510 % 978, solution to part (c2). -MC 2/7/09

Delete the 'm' that is after the 1/2 and before the big square brackets

Problem 10.63.b, page 561. -AN 2/17/09

Change “F(r) = -GMm / (r^2)" to “F(r)
= GMm / (r^2)” (delete the - sign).

Prob 13.15, page 713. - AA 3/5/09

Change Phi_dot_zero to Theta_dot_zero.

Prob 14.52, page 816, 3rd line - LL 4/9/09

Delete the words "frictionless but".

Prob 14.56, page 817, 3rd line. -KH 3/29/09

Change "... s back and forth" to "...
rocks back and forth".

*Prob 15.38, p886 -NR, 12/21/08:

"Find the angular velocity and acceleration theta dot and theta double
dot" should be

"Find the angular velocity and acceleration phi dot
and phi double
dot"

*Prob 16.12c, p945 -DH, 12/21/08:

Add this text to problem statement "Assume theta naught = 0."

**Errors in Samples
**Sample 4.19, Section 4.5, page 230, Figure 4.73, -ABR 3/22/09

Point B is at the cross, a= 1 ft, b = 3 ft.

Sample 6.6, Section 6.2, page 336.
-MC 1/19/09:

Fig 6.37 is missing the suitcase height h= 30 cm.

Fig 6.37 the handle on the side, indicating COM, should be in the middle.

Fig 6.38 the reaction R should be vertical.

Calculation is wrong: a) neglects h, b) incorrectly assumes cos(30 deg) =
1/2.

Sample 9.1, section 9.1, pg 412, final answers. -TB 1/28/09

v should be 12 m/s (not 8 m/s) and accelation should be 4 m/s^2 (not 2 m/s^2).

Sample
9.9, Section 9.2, pg 431, 4 lines below "Solution
4 - Work Energy" - PA 1/27/09

Change "
- F i = - ma i" to "
- F i = ma i" .

Sample 9.3, Section 9.1, page 414. -RS 1/21/09

Change "knots per hour" to "knots" or "nuatical miles per
hour".

Sample 9.27, Section 9.5, pg 483. -VS 2/5/09

Wording could be misinterpretted. Less ambiguous wording would be:

"A metal ball .. strikes
a stationary surface S1 with velocity v = 10m/s(i) and rebounds with velocity
v = -9m/s(i). In a later experiment the same ball strikes another stationary
surface S2 with the same velocity v = 10m/s(i) and again rebounds with
velocity v = -9m/s(i)."

Sample 9.28, Section 9.5, pg. 484, eqn 9.74. -JH 2/10/09

Change (1+Me2) to (Me2-1).

Sample 9.28, Section 9.5, pg. 484 -VS 2/5/09

In the paragraph titled "Collision-2:", third line is missing minus sign:

Change "... to be v1- = sqrt(2gh)." to "...
to be v1- = -sqrt(2gh)."

Sample 10.5, Section 10.1, pg 529, 4th eqn from bottom. -SR 2/24/09

Change tan^(-1)(xdot/ydot) to tan^(-1)(ydot/xdot).

Sample 11.1, Section 11.1, page 569, 3rd eqn, just above "Similarly, " -EB
4/4/09

Change "7.25 kg m" to "7.5
kg m"

And 3 lines down

Change "8.55 kg m" to "8.5
kg m"

And the last 2 lines on the page, two times,

Change "...+0.5m/s*j"
to "...-0.5m/s*j" (sign error in y component)

Sample 11.2, Section 11.1, page 571, paragraphs numbered 3 and 4. -JP 2/18/09

Should refer to figs 11.7 and 11.8, respectively. Not to11.6 and 11.7.

Sample 12.4, Sect 12.1, pg 597 -KL 6/20/09

First line of equations under "Linear Momentum balance for mass A gives".

Change (2T - F)i + (2Na - mg) = (-ma)i to (2T
- F)i + (2Na - mg) = (ma)i

(Get rid of wrong minus sign.)

Sample 13.2, Section 13.1, page 634, 2nd column of table. -BF 3/18/09

Change 2.29 rad/s to 6.05 rad/s.

Sample 13.3, Section 13.1, page 636, Figure 13.15 caption. -EB 3/29/09

Change k = - 0.1/s to k
= 0.1/s. (delete minus sign).

Sample 13.7, Section 13.2, page 646, 2nd line. -EB 3/29/09

Change 200 cm to 200
mm.

Sample 13.7, Section 13.2, page 646, 2nd to last line of calculation on page.
-EB 3/29/09

Change 0.02 kg to 0.05
kg.

Sample 13.17, Sect 13.4, pg 669. -KL 6/20/09

The first line of equations under part (ii).

Change ... - w^2 to - w^2 L jhat

Sample 14.5, Section 14.1, pg 750, 2nd to last line of eqn 14.15 -RM 4/2/09

Change
"+l*(thetadot^2)*sin(theta)ihat" to "-l*(thetadot^2)*sin(theta)ihat".

(Sign error typo. The term is correct in the lines above and below this error.)

Sample 14.5, Section 14.1, pg 750, last line of eqn 14.15 -RM 4/2/09

Change "((thetadotdot)^2)*cos(theta)jhat" to "((thetadot)^2)*cos(theta)jhat".

(Typo, extra dot on a thetadot term.)

Sample 14.7, sect 14.2, pg 763, - TG 3/23/09

Just under
'We can easily
solve the equations of motion to get"

Change ...y0dot - (1/2)*g*t^2 to ...y0dot*t - (1/2)*g*t^2.

(That is, multiply the y0dot term by t)

Sample 14.18, sect 14.4 pg 786 - ME 6/20/09

Last line before "Comments".

Change "replacing xdotdot with thetadotdot*R"
to "replacing xdotdot with -thetadotdot*R".

(Theta is positive when CCW, as per sample 14.17).

Sample 14.18, sect 14.4 pg 786 - ME 6/20/09

Last unshaded eqn.

Change "thetadotdot = FR cos phi ..."
to "thetadotdot = (F/R) cos phi ..."

(Divide present answer by R^2).

Sample 15.5, Section 15.2, pg847, 3rd line from bottom. -ME 6/20/09

Change
"ap = =a/tube jhat+ ..." to "ap
= - a/tube jhat + ..."

Sample 15.6, Sect 15.2, p.848. Blue shaded box. -ME 6/20/09

Change “ethetadot = omega er” to “ethetadot
= - omega er".

(Need to add missing minus sign.)

* Sample 15.15, Section 15.5, p880 (3rd paragraph, 3rd line) -NR, 12/21/08:

"(i) by considering rod CD" should be "(i) by considering rod
CB"

**Errors in Text, Shaded Boxes, etc. **

Section 2.1, p43, eqn above "Position relative to the origin". -PA 1/28/09

Change "r sub B/A = -r sub B/A" to
"r sub B/A = -r sub A/B".

*Section 2.1, p43, caption to Figure 2.8. -AR 1/5/09

In the phrase `... the symbol v r is defined..' the 'v r' should be

a boldface r with an arrow on top.

Section 3.2, page 171: "critique of coulomb friction." -MS 6/16/09

Change
"F independent of A <--> F independent of N" to "F
independent of A <--> F proportional to N"

Also change "situations which" to "situations in which".

Section 5.2, p 262, Fig 5.23a, -AR 3/27/09

The box should not be shaded. Its 4 bars in a square.

Sect 9.1, pg 400, Figure 9.4 caption -MCh 1/27/09

Change "1000 m" to "1000 s".

Sect 9.1, Pg. 405, "Poundal" Paragraph, 3rd line. -EB 1/27/09

Change "1 pdl = 1 lbm ft/s" to "1 pdl = 1 lbm ft/s^2"

Section 9.1, Pg. 405, Section 9.1, “Poundal” Paragraph, 4th line,
-AN 1/23/09

Change “... Newtons
are to the English.” to “... Newtons are
to the ‘metric’/SI.”

Sect 9.1, pg. 408, box 9.2, 2nd par, 5th line. -EB
1/27/09

Change d^2/dt^2 = u' ' to d^2
u/dt^2 = u' '.

Sect 9.1, pg 410, eqn below "Carrying out the integrals..." -EB
1/27/09

Change "-ct =..." to "ct = ... ".

Section 9.2, pg 424, 2nd line from bottom. -JBR 1/27/09

Change "F=kx, " to "(force on the mass of) F = -kx, "

Section 9.3, pg 441, 2 lines above box 9.5. -JS 1/27/09

change "2 cm, 1 cm," to
"2 cm,".

Section 9.3, pg 442, 1 line above giant square root. -JS 1/27/09

Change "k=5 N/m" to "k=50 N/m".

Section 9.3, pg 447, box 9.6, 2nd sentence of "Overdamped" section. -JBR 2/4/09

Change "equation refoverdame" to "equation 9.28".

Section 9.4, pg. 464, paragraph above `Example: Matrix form:' -JBR 2/4/09

Change one occurance of "row 17 column 9" to "row 7 column
19 "

and the other to
"row 19 column 7 ".

Section 9.4, pg. 464, Example: Matrix form, big equation. JBR -2/4/09

In the x column matrix, the entries (xA, xB, xD) should not have double dots
on top.

Section 9.4, pg 470, figure 9.55. -PA 1/30/09

Change k1(x2 - x1) to
k2(x2 - x1).

Section 10.3, pg 547, eqn 10.18. Typo. -AN 2/10/09

There should be a one on top of the fraction under the radical.

(Also, in case its not clear, the r^(3/2) is outside the radical.)

Section 12.2, pg 606, 12.2, "How wheels ... " paragraph, 5th line. -AN 2/23/09

Change 3.33 and 3.33 to 3.33a
and 3.33b, respectively.

Section 13.1, pg 630, Figure 13.8 caption. - AN 3/18/09

The last equation in the caption has a wrong left hand side.

Change
“(e theta hat) = ..." to "(j
hat) = ...".

Sect 13.2, pg 640, last eqn in "Linear momentum balance in polar coordinates" section.
-EB 3/29/09

Change "a_r = theta_dot ^2*r = v^2/r" to "a_r=
-theta_dot^2*r= - v^2/r". (add two minus signs)

Section 13.3, Page 651, box 13.3, 2nd column, 1st par, last line. -ABR 1/21/09

Change "both BA and VC" to "both BA and AC".

Sect 13.3, pg 653, Eqn 13.24, 2nd line. -EB 3/29/09

Change " sin(theta)*i' cos(theta)*j' " to " sin(theta)*i' + cos(theta)*j' "

(Insert a "+" sign).

Sect 14.1, pg 740, First set of equations on page. -EB 5/11/09

In all three equations change the second appearance of x' to
y'.

Sect 14.4, p.782, first eqn below "Does the ball slide?" -ME
6/20/09

Change
"AMB (Ftot=m*aG)" to "LMB
(Ftot=m*aG)".

*Section 14.4, p782, third line below "Does the ball slide?" -NR,
12/21/08

Change
"Use linear momentum balance to..." to "Use
angular momentum balance to...".

Section 14.4 p.783. 2nd paragraph. -ME 6/20/09

Change "(using
er x et = k)" to "(using er x etheta = k)"

Sect 14.4, pg 783, the next eqn. -AR 6/20/09

Change g sin theta to -g
sin theta.

(Make whole right hand side negative.)

Sect 14.4, pg 783, the next eqn. -KL 6/20/09

Change "... theta" to "...theta
= 0".

(Set whole expression to zero)

Sect 14.4, pg 783, the last paragraph. -AR 6/20/09

Delete "or AAA battery".

(A cylinder has a different inertia than a sphere.)

*Section 14.1, p737 (Fig 14.5) -NR, 12/21/08:

Two vectors are labeled r sub P/O. The short one of them (from O to original
P) should be r sub P/O superscript .

Section 15.1, pg 830, 2nd to last eqn. -ME 6/20/09

Change "eb = et x eb" to "eb
= et x en"

*Section 15.3, page 854, 3rd line of equations. -ML 3/27/09

Change omegadot_B cross
r_P/O to omegadot_B
cross r_P/O'
.

(It should be the position of P with respect to O'.)

Sect 16.2, p.915. Pendulum Example, 2nd to last eqn. -ME -6/20/09

Change "-gl("
to "-mgl(".

(Insert the missing m).

Sect 16.2, p.919, Eqn 16.33. -ME 6/20/09

Change thetadotodot to theta, and

Change theta to
thetadotdot.

Section 16.3, pg 930, Example "A two link..." -BF 5/4/09

Change all occurances of -mg j to +mg
i.

---------------------

Send comments to ruina@cornell.edu.