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Transcript 
Chapter 4 continued
a. Draw a free-body diagram for the
elevator.
FT
Fg
b. What is the tension in the cable that
provides the upward force on the
elevator car?
Fnet ! FT " Fg ! ma
FT ! ma # Fg
! (1250 kg)(2.5 m/s2) #
(1250 kg)(9.80 m/s2)
! 9100 N upward
10. Ngan has a weight of 314.5 N on Mars and
a weight of 833.0 N on Earth.
12. During a space launch, an astronaut typically
undergoes an acceleration of 3 gs, which
means he experiences an acceleration that
is three times that of gravity alone. What
would be the apparent weight of a 205-kg
astronaut that experiences a 3-g liftoff?
Let up be the negative direction.
Fnet ! Fg, apparent " Fg ! ma
Fg, apparent ! Fg # ma
! (205 kg)(9.80 m/s2) #
(205 kg)(3)(#9.80 m/s2)
! 8040 N
13. Alfonso and Sarah like to go sky diving
together. Alfonso has a mass of 88 kg, and
Sarah has a mass of 66 kg. While in free fall
together, Alfonso pushes Sarah horizontally
with a force of 12.3 N.
a. What is Ngan’s mass on Mars?
Fg, Earth ! mgEarth
Fg, Earth
833.0 N
! ! !!
m! !
2 ! 85.0 kg
gEarth
9.80 m/s
b. What is the acceleration due to gravity
on Mars, gMars?
Mars
! mgMars
Fg, Mars
314.5 N
! ! !
gMars ! !
m
85.0 kg
! 3.70 m/s2
11. Alex is on the wrestling team and has a mass
of 85.3 kg. Being a whiz at physics, he realizes that he is over the 830.0-N cutoff for his
weight class. If he can convince the trainers
to measure his weight in the elevator, what
must be the acceleration of the elevator so
that he just makes his weight class?
Fnet ! Fg, apparent " Fg ! ma
Fg, apparent " Fg
a ! !!
m
830.0 kg " (85.3 kg)(#9.80 m/s2)
85.3 kg
! !!!!
! #0.0696 m/s2
a ! 0.0696 m/s2 down
604
Solutions Manual
Fon Sarah ! mSarahaSarah
Fon Sarah
aSarah ! !!
mSarah
12.3 N
! ! ! 0.19 m/s2
66 kg
b. What is Sarah’s horizontal acceleration?
Fon Alphonso ! Fon Sarah
! mAlphonsoaAlphonso
Fon Alphonso
12.3 N
aAlphonso ! !! ! !
mAlphonso
88 kg
! 0.14 m/s2
14. A 7.25-g bullet is fired from a gun. The
muzzle velocity of the bullet is 223 m/s.
Assume that the bullet accelerates at a
constant rate along the barrel of the gun
before it emerges with constant speed.
The barrel of the gun is 0.203 m long.
What average force does the bullet exert
on the gun?
by Newton’s third law
Fon bullet ! Fon gun
Physics: Principles and Problems
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Fg,
a. What is Alfonso’s horizontal acceleration?
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