PHYSICS, EXTENDED 12TH EDITION BY DAVID
HALLIDAY (AUTHOR), ROBERT RESNICK
(AUTHOR), JEARL WALKER (AUTHOR)-
QUESTIONS WITH DEATAILED SOLUTIONS| A+
,1. The Speed (Assumed Constant) Is (90 Km/H)(1000 M/Km) (3600 S/H) = 25 M/S.
Thus, During 0.50 S, The Car Travels (0.50)(25) 13 M.
,2. Huber’s Speed Is
V0=(200 M)/(6.509 S)=30.72 M/S = 110.6 Km/H,
Where We Have Used The Conversion Factor 1 M/S = 3.6 Km/H. Since Whittingham
Beat Huber By 19.0 Km/H, His Speed Is V1=(110.6 + 19.0)=129.6 Km/H, Or 36 M/S (1
Km/H = 0.2778 M/S). Thus, The Time Through A Distance Of 200 M For Whittingham
Is
X 200 M
T = = = 5.554 S.
V1 36 M/S
, 3. We Use Eq. 2-2 And Eq. 2-3. During A Time Tc When The Velocity Remains A
Positive Constant, Speed Is Equivalent To Velocity, And Distance Is Equivalent To
Displacement, With X = V Tc.
(a) During The First Part Of The Motion, The Displacement Is X1 = 40 Km And The
Time Interval Is
(40 Km)
T1 = = 1.33 H.
(30 Km /
H)
During The Second Part The Displacement Is X2 = 40 Km And The Time Interval Is
(40 Km)
T2 = = 0.67 H.
(60 Km /
H)
Both Displacements Are In The Same Direction, So The Total Displacement Is
X = X1 + X2 = 40 Km + 40 Km = 80 Km.
The Total Time For The Trip Is T = T1 + T2 = 2.00 H. Consequently, The Average Velocity
Is
(80 Km)
Vavg = = 40 Km / H.
(2.0 H)
(b) In This Example, The Numerical Result For The Average Speed Is The Same As
The Average Velocity 40 Km/H.
(c) As Shown Below, The Graph Consists Of Two Contiguous Line Segments, The First
Having A Slope Of 30 Km/H And Connecting The Origin To (T1, X1) = (1.33 H, 40
Km) And The Second Having A Slope Of 60 Km/H And Connecting (T1, X1) To (T, X) =
(2.00 H, 80 Km). From The Graphical Point Of View , The Slope Of The Dashed
Line Drawn From The Origin To (T, X) Represents The Average Velocity.