Transcription of CHAPTER 4 Forces in One Dimension
1 Physics: Principles and ProblemsSolutions Manual61 Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, in One DimensionCHAPTERP ractice and Motionpages 87 95page 89 For each of the following situations, specify the systemand draw a motion diagram and a free-body dia-gram. Label all Forces with their agents, and indicatethe direction of the acceleration and of the net vectors of appropriate flowerpot falls freely from a windowsill.(Ignore any Forces due to air resistance.) sky diver falls downward through the airat constant velocity. (The air exerts anupward force on the person.)
2 Cable pulls a crate at a constant speedacross a horizontal surface. The surface pro-vides a force that resists the crate s rope lifts a bucket at a constant speed.(Ignore air resistance.) rope lowers a bucket at a constant speed.(Ignore air resistance.) vvvvFrope on bucketFEarth s mass on bucketFnet ! 0a ! 0"ySystem"yvvvvFrope on bucketFEarth s mass on bucketFnet ! 0a ! 0 System"xva ! 0 Fnet ! 0 Fpull on crateFfriction on cratevvvSystem"yvvvFEarth s mass on diverFair resistance on divera ! 0 SystemFnet ! 0"yFEarth s mass on flowerpotvaSystemFnetpage horizontal Forces , 225 N and 165 N,are exerted on a canoe.
3 If these Forces areapplied in the same direction, find the nethorizontal force on the canoe. Fnet!225 N"165 N ! #102N in the direction of the two the same two Forces as in the previousproblem are exerted on the canoe in oppo-site directions, what is the net horizontalforce on the canoe? Be sure to indicate thedirection of the net !225 N$165 N ! #101N in the direction of the larger confused sleigh dogs are trying topull a sled across the Alaskan snow. Alutiapulls east with a force of 35 N, Seward alsopulls east but with a force of 42 N, and bigKodiak pulls west with a force of 53 is the net force on the sled?
4 Identify east as positive and the sled asthe !FAlutia on sled"FSeward on sled$FKodiak on sled!35 N "42 N $53 N !24 N Fnet!24 N eastSection and Motionpages 87 95page each of the following aseither a, b,or c:weight, mass, inertia, thepush of a hand, thrust, resistance, air resis-tance, spring force, and acceleration. contact field force a forceweight (b), mass (c), inertia (c), push ofa hand (a), thrust (a), resistance (a),air resistance (a), spring force (a), accel-eration (c) you feel the inertia of a pencil?Of a book? If you can, describe , you can feel the iner tia of eitherobject by using your hand to give eitherobject an acceleration; that is, try tochange the objects DiagramDraw a free-body dia-gram of a bag of sugar being lifted by yourhand at a constant speed.
5 Specifically identifythe system. Label all Forces with their agentsand make the arrows the correct of VelocityIf you push a bookin the forward direction, does this mean itsvelocity has to be forward?No, it could be moving backward andyou would be reducing that DiagramDraw a free-body dia-gram of a water bucket being lifted by a ropeat a decreasing speed. Specifically identifythe system. Label all Forces with their agentsand make the arrows the correct on bucketFEarth s mass on bucketSystemaSugarFhand on bagFEarth s mass on bagSystema ! 062 Solutions ManualPhysics: Principles and ProblemsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continuedPhysics: Principles and ProblemsSolutions Manual63 Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, ThinkingA force of 1 N is theonly force exerted on a block, and the accel-eration of the block is measured.
6 When thesame force is the only force exerted on asecond block, the acceleration is three timesas large. What can you conclude about themasses of the two blocks?Because m!F/aand the Forces are thesame, the mass of the second block isone-third the mass of the first Newton s Lawspages 96 101page place a watermelon on a spring scale atthe supermarket. If the mass of the watermel-on is kg, what is the reading on the scale?The scale reads the weight of the water-melon:Fg!mg!( kg)( m/s2) !39 is learning how to ice-skate. Shewants her mother to pull her along so thatshe has an acceleration of m/s2.
7 IfKamaria s mass is kg, with what forcedoes her mother need to pull her? (Neglectany resistance between the ice andKamaria s skates.) Fnet!ma!( kg)( m/s2) !22 and Reiko simultaneously grab piece of rope and begin tugging onit in opposite directions. If Taru pulls witha force of N and the rope acceleratesaway from her at m/s2, with whatforce is Reiko pulling?Identify Reiko s direction as positiveand the rope as the !FRieko on rope$FTa r u o n ro p e!maFRieko on rope!ma"FTa r u o n ro p e!( kg)( m/s2)" N!17 Figure 4-8,the block has a mass of kg and the sphere has a mass of are the readings on the two scales?
8 (Neglect the masses of the scales.) Figure 4-8 Bottom scale: Identify the sphere as thesystem and up as !Fscale on sphere$FEarth s mass on sphere!ma!0 Fscale on sphere!FEarth s mass on sphere!msphereg!( kg)( m/s2)!29 NTop scale: Identify the block as the sys-tem and up as !Ftop scale on block$Fbottom scale on block$FEarth s mass on block!ma!0 Ftop scale on block!Fbottom scale on block"FEarth s mass on block!Fbottom scale on block"mblockg!29 N "( kg)( m/s2)!41 NChapter 4 continuedpage Earth, a scale shows that you weigh 585 is your mass?The scale reads 585 N. Since there isno acceleration, your weight equalsthe downward force of gravity:Fg!
9 Mgso m!!! would the scale read on the Moon(g! m/s2)?On the moon,gchanges:Fg!mgMoon!( kg)( m/s2) ! the results from Example Problem 2 toanswer questions about a scale in an eleva-tor on Earth. What force would be exertedby the scale on a person in the followingsituations? elevator moves at constant speed, so a!0 and Fnet! !Fg!mg!( kg)( m/s2) !735 slows at m/s2while while moving upward, so a!$ m/s2 Fscale!Fnet"Fg!ma"mg!m(a"g)!( kg)($ m/s2" m/s2) !585 speeds up at m/s2while downward,so a!$ m/s2 Fscale!Fnet"Fg!ma"mg!m(a"g)!( kg)($ m/s2" m/s2) !585 moves downward at constant speed, so a!
10 0 and Fnet!0 Fscale!Fg!mg!( kg)( m/s2) !735 slows to a stop at a constant magni-tude of acceleration !a,thoughthe sign of adepends on the direc-tion of the motion that is !Fnet"Fg!ma"mg!( kg)(a) "( kg)( m/s2) !( kg)(a) "735 N585 N"" m/s2Fg"g64 Solutions ManualPhysics: Principles and ProblemsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continuedPhysics: Principles and ProblemsSolutions Manual65 Copyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Newton s Lawspages 96 101page GravityCompare the force holdinga rock on Earth and on the acceleration due to gravity on theMoon is hold the rock on Ear th:Fnet!