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補史名www asftrppfysfts 600)
For Thoughtand Diseussion
tneuish the Aristotelian and Galilean/Newtonian views ofihe
ball bounees ofrawall with the same speedithad beforeithit
Wall Has its momentum changed? Hasaforoe acted on the
2 Has aforee acted on the wall? Relate your answers to New
aws of motion
ten use the term "inertias to deseribe human sluggishness
5this usage related to the meaning ofFsinertiae in physics?
does aceiling fan continue to rotate even after you have
vitched it ofP?
Wek erashes into a Stalled cear A student trying to explain the
es ofthis event claims thar no forees are involved: the car
Tin the way”so itgot hit Commen
foot astronaut kicks a ball, hard, across aspace station
balls apparent weightlessness mean he astronauts toes
下avity on Jupiters moon Io is one-fifth that on
Would happen te your weight and to your mass if
nIo?
tis the direcetion of momentum oFamoving body? Does it
Fthe body:
plane aceelerates down the munway, you take your keys
r poeket and suspend them by a thread. Do they hang
force from the chairon you.
iir? Hnot, what forees are
fxerrisesaned Problems 85 $
還2620Groeoeoeardaoeos WiA poaor Wonoeno0 Op ir oa
20。 Staring frorm rest and undergoing constan acceleratiom,a920-kg
ar covers 410 min $.15 8. Find the foree on the car
21 dropping dontest, a student encatses am 83-g cgg in
large Styrofoam block. fs g emn'texceed 2.0N
and 計the bloek hits the g pow mueh must
the Styror jompress on impaet) Note: The aceelei
assoeialed with stOppi
gravity while the Styrofe
the ground.
22. Inatront-end collision, a 1400-kg car with shockzabsorbing bump:
ems can withstand amaximum force of 75kN before damage Gccurs:
Hthe maximum speed foranondamaging collision is 9.0 kmzh, by
Bow much must he bumper be able to move relative to the car?
section 4.4 The Force ofGravity
23。 Show that the units of aceeleration can be written as N/kg- Why
doesitmake sense to give gas 9.8 N/kg when talking about imass
and weight?
24. Your spaceship crashes on one of the Sun's planets, Fortunately 上
the ship's scales are intact and show that your weightis 680 N.H
your mass is 58 kg, where are you? (imr: Consult AppendixEE)
Your friend can barely lift a 35-kg concrete block on E:
massive ablock could she lift on the Moon?
26 Acereal box says "net weight 350 grams” Whats the actual
Weight ta in SLunits and (b) in ounees?
27. Youre asafety engineerforabridge spanning the U,S-Canadian
border. U.S. speeifications permit a maximum load of 10 tons
What load iimit should you speeify on the Canadian side. where
welght is given in kilograms?
28.。 The gravitational acceleration atthe lntermational Space Stations
altitude is about 91凶 oFits surface value. Whats the weightofa
64-kg astronaut atthis altitude?
ection 4.5 Using Newton's SecondLaw
A 50-kg parachutist deseends atasteady 40 km/h. What foree
does air exert on the parachute?
30, A 960-kg motorboat accelerates away from adock at2.1 m/s
Its propellerprovides a3.9-kN thrust force. What drag force does
the water exert on the boat?
An elevator aceelerates downward at2.4 ms. What force does
the elevator's floor exertona52-kg passengery
32. At 560 metric tons, the Airbus A-380 is the World's largest air-
liner Whats the upward force on an A-380 when the plane is
(am flying at constant altitude and (b) aceelerating upward at
15m/s2?
33. Yourre an engineer working on Ares 1 NASAs replacement tor
the space Shuttles. Performance speces call for afirst-stage TOcket
Gapable ofaccelerating atotal mass 0f 600 Me vertically ftom
Testt0 7700 km in 1.7 min. Youre asked to determine tbe re-
quired engine thrust (force) and the foree exerted ona79-kg as-
tronaut during Tiftoff. What do you Teport?
34. You step into an elevatorand itacceleratesto adownward speed
gfF8.8 mAS in 2.4 5 Quantitatively compare your apparent weight
during thistime with youracetual weight,
44.6 NewtonsThirdLaw
ional foree does 3 5600-kg elephant exer
必
63. she jumps ofta140-emhi過台
人 rdheras she falls?
