1. Which One Of The Following Statements Concerning .

PHY231 Section 2, Form AMarch 22, 20121. Which one of the following statements concerning kinetic energy is true?A)B)C)D)E)Kinetic energy can be measured in watts.Kinetic energy is always equal to the potential energy.Kinetic energy is always positive.Kinetic energy is a quantitative measure of inertia.Kinetic energy is directly proportional to velocity.2. A man jumps from the roof of a tall building, but is unhurt because the person landson an air-filled bag. Which one of the following best describes why no injury occurs?!p F!t " F !p !t ; !t increases, F decreasesA) The bag provides the necessary force to stop the person.B) The bag reduces the impulse to the person.C) The bag increases the amount of time the force acts on the person and reduces thechange in momentum.D) The bag decreases the amount of time during which the momentum is changing andreduces the average force on the person.E) The bag increases the amount of time during which the momentum is changing andreduces the average force on the person.3. A tennis ball has a velocity of 12 m/s downward just before it strikes the ground andbounces up with a velocity of 12 m/s upward. Which statement is true concerning thissituation?Momentum is a vector! Ball collides with Earth.Momentum of the system (Ball Earth) remains constant.Ball's momentum vector changes : vB,0 !12 m/s; vB,f 12 m/sTherefore, Earth's momentum must also change.A)B)C)D)E)The momentum of the ball and the momentum of the earth both change.Neither the momentum of the ball nor the momentum of the earth changes.The momentum of the ball is changed; and the momentum of the earth is not changed.The momentum of the ball is unchanged; and the momentum of the earth is changed.Both the momentum and the kinetic energy of the ball change because of the collision.4. A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. Thetension in the rope is 40 N; and the net work done on the block is 211 J. What angle doesthe rope make with the horizontal?s 7.0m, T 40 N, W 211 J;A)B)C)D)E)W Fs (T cos! ) s;28 41 47 62 88 #W &! cos "1 % ( Ts '1#&211 J cos "1 %( 41 ( 40 N ) (7.0 m) '

PHY231 Section 2, Form AMarch 22, 20125. The kinetic energy of a car is 8 106 J, as it travels along a horizontal road. Howmuch power is required to stop the car in 100 s?A)B)C)D)E)zero watts8 104 W8 105 W8 106 W8 107 WE 8 ! 106 JPower 8 ! 104 Wt100s6. At a specific time, an object moving on a circle of radius 5.0 m, experiences a centripetalacceleration of 2.0 m/s2, and an angular acceleration of 0.70 rad/s2. What is the total linearacceleration of the object?A)B)C)D)E)2.5 m/s22.9 m/s23.2 m/s24.0 m/s24.5 m/s2aC 2.0 m/s 2 , ! 0.70 rad/s 2 , r 5.0 maT ! r 3.5 m/saaT2a aT2 a C2 (3.5)2 (2.0)2 m/s 4.0m/saC7. Three objects are attached toa massless rigid rod that has anaxis of rotation as shown.Assuming all of the mass ofeach object is located at thepoint shown for each, calculatethe moment of inertia of thisA) 1.3 kg m2B) 3.1 kg m2C) 5.3 kg m2D) 7.2 kg m2E) 9.1 kg m2I ! mr 2 (2.0 kg)(1.0 m) 2 (1.0 kg)(2.0 m) 2 (0.5 kg)(2.5 m) 2() 2 4 3.1 kg " m 2 9.1kg " m 28. A 5.00-kg block of ice is sliding across a frozen pond at 10.00 m/s. A 7.60-N force isapplied opposite to the direction of motion. After the ice block slides 15.0 m, the force isremoved. The work done by the applied force isA)B)C)D)E)–114 J. 114 J.–735 J. 735 J. 19.7 JW Fs (!7.60 N)(15.0m) –114J2

PHY231 Section 2, Form AMarch 22, 20129. A rock is dropped from a high tower and falls freely under the influence of gravity.Which one of the following statements concerning the rock as it falls is true? Neglect theeffects of air resistance.!p F!t ( mg ) !tA) The rock will gain an equal amount of kinetic energy during each second.B) The rock will gain an equal amount of momentum during each second.C) The rock will gain an equal amount of speed for each meter through which it falls.D) The rock will gain an equal amount of momentum for each meter through which itfalls.E) The amount of momentum the rock gains will be proportional to the amount ofpotential energy that it loses.10. A bicycle travels 282 m along a circular track of radius 30 m. What is the angulardisplacement in radians of the bicycle from its starting position?A)B)C)D)E)1.0 rad1.5 rad3.0 rad4.7 rad9.4 rad! s 282 m 9.4 radr 30 m11. A child standing on the edge of a freely spinning merry-go-round moves quickly tothe center. Which one of the following statements is necessarily true concerning thisevent and why?A) The angular speed of the system decreases because the moment of inertia of thesystem has increased.B) The angular speed of the system increases because the moment of inertia of thesystem has increased.C) The angular speed of the system increases because the moment of inertia of thesystem has decreased.D) The angular speed of the system decreases because the moment of inertia of thesystem has decreased.E) The angular speed of the system remains the same because the net torque on themerry-go-round is zero N m.No external torque: angular momentum conserved()I 0! 0 I f ! f ; ! f I 0 I f ! 0Moment of inertia decreases: I 0 I f ! speed increases: ! f ! 03

PHY231 Section 2, Form AMarch 22, 201212. A string is wrapped around a pulley!" of radius 0.05 m and moment of inertia 0.4 kg m2. If the string is pulled with a force F , the resulting!" angular acceleration of the pulley2is 2 rad/s . Determine the magnitude of the force F .A) 0.4 N! I" ; ! FR; # FR I"B) 2 NC) 8 N0.4 kg m 2 (2 rad/s 2 )I"D) 16 NF 16 NR0.05mE) 40 N()A block of mass m is released from rest at a height R abovea horizontal surface. The acceleration due to gravity is g.The block slides along the inside of a frictionless circularhoop of radius R13. Which one of the following expressions gives the speedof the mass at the bottom of the hoop?A)B)C)D)E)zero m/s2v mgRv mg (2R)v2 2gRv2 g 2 RmgR 12 mv 2v 2 2gR14. For the mass in the problem above, what is the magnitude of the normal forceexerted on the block by the hoop when the block reaches the bottom of the hoop?A)B)C)D)E)zero newtonsmg2/R3mg2mg1mgv22gRFC maC m mRRFC F! " mg 2mg; F! 3mgW mgF!15. A certain string just breaks when it is under 54 N of tension. A boy uses this stringto whirl a 0.75-kg stone in a horizontal circle of radius 2.0 m. The boy continuouslyincreases the speed of the stone. At approximately what speed will the string break?A)B)C)D)E)6.4 m/s8.2 m/s12 m/s15 m/s18 m/sFbreak 54 N, m 0.75N, R 2.0 mFC Fbreak ;v2m FbreakRFC maC m! v 4v2;rFbreak R(54 N)(2.0m) 12 m/sm0.75 kg

PHY231 Section 2, Form AMarch 22, 201216. Two boxes are connected to eachother as shown. The system is releasedfrom rest and the 1.00-kg box fallsthrough a distance of 1.00 m. Thesurface of the table is frictionless. Whatis the kinetic energy of box B just beforeit reaches the floor?A)B)C)D)E)2.45 J4.90 J9.80 J29.4 J39.2 J1.00 kg1.00 kg1.00 mPEA (constant); PEB0 mB gh 9.8 J; PEfB 0KEf PEf KE0 PE012(mA mB )v 2 PEB0KEf 12 mBv 2 ! v2 2PEB0mA mBmB1PEB0 9.8 J 4.90 JmA mB217. A 200-kg cannon at rest contains a 10-kg cannon ball. When fired, the cannon ballleaves the cannon with a speed of 90 m/s. What is the recoil speed of the cannon?A)B)C)D)E)4.5 m/s9 m/s45 m/s90 m/szero m/smc 200 kg, mb 10 kg, vb 90 m/s.Pf P0 ; mb vb mc vc 0; vc mb10vb 90 m/s 4.5m/smc200()18. A car enters a horizontal, curved roadbed of radius 200 m. The coefficient of staticfriction between the tires and the roadbed is 0.20. What is the maximum speed withwhich the car can safely negotiate the unbanked curve?µ 0.20, R 200.0 mA) 5 m/sv2B) 10 m/sF! mg; Ff µ F! ; maC m ;rC) 20 m/s2D) 40 m/svm µ mg " v µ gR 0.20(9.8 m/s 2 )(200m) 20 m/sE) 100 m/sR5

PHY231 Section 2, Form AMarch 22, 201219. A string is tied to a doorknob 0.50 m fromthe hinge as illustrated in the figure. At theinstant shown, the force applied to the string is5.0 N. What is the magnitude of the torque on thedoor?A)B)C)D)E)2.1 N m3.0 N m1.0 N m0.78 N m0.60 N m! F! L ( F sin ! ) L (5.0 sin 57 ) 0.50 N " m 2.1N " m20. In which one of the following situations is zero net work done?A)B)C)D)E)v constant, !KE 0A ball rolls down an inclined plane.Net work: Wp W f !KE 0A physics student stretches a spring.A box is pulled across a rough floor at constant velocity.A projectile falls toward the surface of Earth.A child pulls a toy across a rough surface causing it to accelerate.6

A 200-kg cannon at rest contains a 10-kg cannon ball. When fired, the cannon ball leaves the cannon with a speed of 90 m/s. What is the recoil speed of the cannon? A) 4.5 m/s B) 9 m/s C) 45 m/s D) 90 m/s E) zero m/s c 18. A car enters a horizontal, curved roadbed of radius 200 m. The coefficient of static