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

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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.

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