Solutions to Homework #3
Chapter 5
10.
Picture the Problem
: The 747 is accelerated horizontally in the direction opposite its motion in
order to slow it down from its initial speed of 27.0 m/s.
Strategy:
Use equation 51 to find the acceleration from the known force and mass, then use
equations 27 and 210 to find the speed and distance traveled.
Solution:
1. (a)
Use equation 51 to find
a
r
:
2.
Use equation 27 to find the final
speed:
3. (b)
Use equation 210 to find the
distance
traveled by the 747 as it slows down:
(
29
(
29
(
29
1
1
0
2
2
27.0
17.8 m/s
7.50 s
168 m
x
v
v
t
∆
=
+
∆ =
+
=
Insight:
The landing speed of a Boeing 747200 is 71.9 m/s (161 mi/h) and it has a specified landing
roll distance of 2,121 m, requiring an average landing acceleration of −1.22 m/s
2
.
16.
Picture the Problem
: The force pushes on box 1 in
the manner indicated by the figure at right.
Strategy:
The boxes must each have the same
acceleration, but because they have different masses
the net force on each must be different.
These
observations allow you to use Newton’s Second Law
for each individual box to determine the magnitudes of
the contact forces.
First find the acceleration of all the
boxes and then apply equation 51 to find the contact
forces.
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 Fall '08
 Ashkenkai
 Physics, Acceleration, Force, Mass, Work, Euclidean vector

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