Answer Key Chapter 4 - Henry County Schools

1 Answer KeyPhysics: Principles and ProblemsSupplemental Problems Answer Key75 Chapter and your bike have a combined massof 80 kg. How much braking force has to be applied to slow you from a velocity of 5 m/s to a complete stop in 2 s?a5}vtff22vtii} m/s2F5ma580 kg3( m/s2)5 2200 opening his parachute, a sky diverwith a mass of kg experiences anupward force from air resistance of 150 net force is acting on the sky diver?Fgravity5mg m/s25882 N downwardFnet5 Fair resistance1 FgravityFnet5150 N1(2882 N) 5 2732 N 5730 N is the sky diver s acceleration?a5}Fmnet}5} }5 large helicopter is used to lift a heatpump to the roof of a new building.

2 Themass of the helicopter is andthe mass of the heat pump is 1500 much force must the air exert onthe helicopter to lift the heat pump withan acceleration of m/s2?Fnet5 Flift1 Fovercome gravity5ma1mg5( kg)( m/s2) 1( kg )( m/s2) upward chains connected to the load eachcan withstand a tension of 15,000 the load be safely lifted at m/s2?Fload5 Flift 1 Fovercome gravity5ma 1mg5( kg)( m/s2) 1( kg)( m/s2) load can be safely liftedbecause the total force on thechains is less than their combinedcapability of a lab experiment, you attach a to a spring scale. You lift the scaleand weight with a constant reading of N.

3 Is the value and direction of theacceleration on the weight? N2( kg)( m/s2) N upwarda 5}Fmnet}5} } far do you lift the weight in thefirst interval?df 5di1vit 1}12}at250 m 1(0 m/s)( s) 1}12}( )( s) a large jet flies at a constant altitude, its engines produce a forward thrust The mass of the plane m/s}}} sCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, is the forward acceleration of theplane, ignoring air resistance?F 5maa 5}mF}5} } much upward force must the airexert on the plane when it is flyinghorizontally?Because the plane is not changingaltitude,Fnet50, soFlift5 2 FgravityFlift5 2 Fgravity5 2( kg)( m/s2) masses are tied to a rope on a pulley,as shown the system is released from thisposition, what is the acceleration of mass?

4 Fnet5Fg-large2Fg-small1mlargeg 2msmallg5( kg)( m/s2) 2( kg)( m/s2) N downwarda5}mF} long does it take for the to fall to the floor?Solve df5di 1vit 1}12}at2for t while di50 m, vi50 m/st5!}2ad} 5!}(42.)2(1m. 5/sm2)} man is standing on a scale inside an airplane. When the airplane is traveling horizontally (in other words, the verticalacceleration of the plane is zero) the scale reads N. What is the verticalacceleration of the plane in each of the following situations? the scale reads (2Fg) the scale reads }Fgg}Fnet5maFnet5 Fscale1(2Fg)( m/s2)( N)}}}} Ng(Fscale2Fg)}}FgFscale2Fg}} 1}Fgg}2 Fscale2Fg}}mFg} N} kgFrictionless mAnswer Key76 Supplemental Problems Answer KeyPhysics: Principles and ProblemsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continuedAnswer KeyPhysics: Principles and ProblemsSupplemental Problems Answer Key77ma5 Fscale2 Fga555}g(FscaFleg2Fg)}55 airboat glides across the surface of thewater on a cushion of air.

5 Perform the following calculations for a boat in whichthe mass of the boat and passengers is 450 there is no friction, how much forcemust the propeller fan exert on the airto accelerate the boat at m/s2?F 5ma 5(450 kg)( m/s2) the actual acceleration with the fangenerating the force calculated in part ais only m/s2, how much frictiondoes the air cushion exert on the boat?afriction5aideal2aactualFfriction5m africtionm(aideal2aactual)(450 kg) 5( m/s2)522 is the upward force exerted by theair cushion on the boat?Flift5 2 Fgravity5 2mg5 2(450 kg)( m/s2) golf ball with a mass of 45 g is struck by a club, leaving the tee with a speed The period of accelerationwas is the average acceleration on theball as it was struck (in m/s2)?

6 A5}vf2tvi}, where vi50 km/ha55} } is the force exerted on the club?F 5ma5(45 g)1}1100k0gg}23( ) is the force exerted on the club bythe ball?Fball5 2 Fclub5 package of instruments is attached to ahelium-filled weather balloon that exerts anupward force of 45 N. the instrument package weighs kg,will the balloon be able to lift it?Flift5maa 5}Fmlift}5} } m/s2 The balloon cannot lift the packagebecause the upward acceleration isless than the downward accelerationof gravity, calculation:Fgravity5( kg)( m/s2) N, which exceeds theupward is the upward acceleration if theinstruments weigh kg?Fnet5 Flift2 FgravityFnet5ma2mg( )1}1100k0mm}21}36100hs}2}}}( ms)1}10010sms}2( m/s2)( N)}}}} NFscale2Fg}} 1}Fgg}2 Fscale2Fg}}mCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continued545 N 2( kg)( m/s2) Na5}Fmnet}5} }513 12-kg block sits on a table.

7 A sits on top of the 12-kg block. If thereis nothing on top of the block, what is the force that the table exerts on the 12-kg block?Ftable5 Fblock 11 Fblock 25(12 kg)( m/s2) 1( kg)( m/s2)5220 box experiences a net force of 41 N whileit is being lifted. What is the acceleration ofthe box? rope can withstand of tension. If the rope is being used to pull a package across a frictionless surface,what is the greatest acceleration that willnot break the rope?F5maa5}mF}5} } weight is attached to a springscale. Find the reading on the scale for eachof the following the scale is not ( kg)( m/s2) the scale accelerates at m/s2in the horizontal vertical component of the acceleration is zero, so the readingon the scale is calculated the sameway as when the scale is not ( kg)( m/s2) penny is dropped from the top of a tower.

8 The tower, however, isnot located on Earth. The penny has a massof g and experiences a gravitationalforce of is acceleration due to gravity onthis planet?ag55511 s, the penny has a velocity m/s. Assuming the force exerted onthe penny by air resistance is uniformand independent of speed, what is themagnitude of the force of air resistanceon the penny?Fnet5maw5Fg1(2Fa)Fa5Fg2ma, where a5aw5}DDvt}5Fg2m1}DDvt} N}} kgFg}m41 N} kgFnet}mAnswer Key78 Supplemental Problems Answer KeyPhysics: Principles and ProblemsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continuedAnswer KeyPhysics: Principles and ProblemsSupplemental Problems Answer Key795Fg2m1}vfD2tvi} N2( kg) NThe air resistance is in the oppositedirection from the force of gravity andthe penny s motion, as it should combined mass of a sled and its rider kg.

9 The sled is pulled across a frozenlake so that the force of friction between thesled and the ice is very that friction between the sledand the ice is negligible, what force is required to accelerate the sled at m/s2?F5 ma5 ( kg)( m/s2)5 force of N is applied to the sled and produces an acceleration of m/s2. What is the magnitude of the force of friction that resists theacceleration? N2( kg)( ms2) m/s}}} sCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, 4 continuedChapter small plane takes off and flies km in a direction southeast of the this point, following the instructions of an air traffic controller, the planeturns to the east of its original flight path and flies km.

10 What is themagnitude of the plane s resultant displacement from the airport?R25 A21B222AB cos uR5 ( )21w( )2w22( kmw)( )(cwos )w5 km hammer slides down a roof that makes a angle with the horizontal. Whatare the magnitudes of the components of the hammer s velocity at the edge ofthe roof if it is moving at a speed of m/s?Fourth quadrant: and vy, cos u5( m/s)(cos ) m/svy5v sin u5( m/s)( )5 Key80 Supplemental Problems Answer KeyPhysics: Principles and ProblemsCopyright Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, KeyPhysics: Principles and ProblemsSupplemental Problems Answer worker has to move a crate along a flat floor in a warehouse.