Ch. 7 8 Exam id A - ID A Physics Honors Ch 7u8 Exam 2014 W...

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Unformatted text preview: ID: A Physics Honors Ch. 7u8 Exam 2014 , W Equations: Wzfi'xcosfi E=W+Uo +12; =Uf+f<ff+§2 13:36 Ug=m§h 1 1 of 2 gap? a; = fie; Q m eflx r: = Em? am 2 MN f5me FArzAfi' mimfim l—mziizofimlvlf+mgiizf vw+vlfwv20+v2f Multiple Choice: Identifii the choice that best completes the statement or answers the question. 1. Which of the following is true when an object of mass m moving on a horizontal frictionless surface hits and sticks to an object of mass M > m, which is initially at rest on the surface? a. The speed of the objects that are stuck together will be less than the initial speed of the less—massive object. The collision is elastic. All of the initial kinetic energy of the less~massive ohect is lost. d. The momentum of the objects that are stuck together has a smaller magnitude than theinitial mmentum of the less—massive object. e. The directon of motion of the objects that are stuck together depends on whether the hit is a head—on collision. .053" to Two people of unequal mass are initially standing still on ice with negligible friction. They then simultaneously push each other horizontally. Afterward, which of the following is true? a The momenta of the two people are of equal magnitude. b. The less massive person has a smaller initial acceleration than the more massive person. c. The speeds of the two people are equal. d The center of mass of the two—person system moves in the direction of the less massive person. e. The kinetic energies of the two people are equal. 3. A tennis ball of mass m rebounds from a racquet with the same speed v as it had initially, as shown below. The magnitude of the momentum change of the bail is a. mv b. 2mvsin6 c. 0 d. 2mv e. 2mvcost9 4. Three objects can only move along a straight, level path. The graphs below show the position 0’ of each of the objects piotted as a function of time I. d d d t I 2 I II III The magnitude of the momentum of the object is increasing in. which of the cases? a. I, II, III (1. 111 only 13. l and III only e. .11 only c. i and H onEy 5. From the top of a high cliff, a ball is thrown horizorrtaiiy with initial speed v0_ Which of the following graphs best represents the bali’s kinetic energy K as a function of time I? b. c. d. e. K K K i 9 WW, 0 I. 0 r 0 I --.—‘—z Use the foilowing information to answer the next two questions. A bali swings freely back and forth in an are from point I to point IV, as shown above. Point If is the lowest point in the path, III is located 0.5 meter above 11, and. IV is 1 meter above Ii. Air resistance is negligibie. 6. if the potentiai energy is zero at point 11, where wiil the kinetic and potential energies of the bail be equai‘? a. At some b. At point 11 c. At point 111 d. At some e. At pointIV point point between H between HE and 1H and IV 7. The speed of the ball at point 1} is most nearly a. M m/s b. 9.8 m/s 0. 20 m/s d. 4.5 m/s e. 3.0 m/s 8. it). The figure below shows a rough semicircular track whose ends are at a vertical height h. T A block placed at point P at one end of the track is released from rest and slides past the bottom of the track. Which of the following is true of the height to which. the block rises on the other side of the track? it is equal to h. it is equal to lit/2. it is between zero and h; the exact height depends on how much energy is lost to friction. It is equal to 11/222”. it is equal to [1/4. snore Two pucks are attached by a stretched Spring and are initially held at rest on a frictionless surface, as shown below. —- ileum-o | X The pucks are then released simultaneously. if puck I has three times the mass of puck 11, which of the following quantities is the same for both pucks as the spring pulls the two packs toward each other? a. acceleration b. speed c. magnitude d. velocity e. kinetic of the energy momentum Two objects of mass 0.2 kg and 0.1 kg, respectively, move parallel to the xmaxls, as shown below. uu~__uln—I—hh The 0.2 kg object overtakes and coliides with the 0.1 kg object. Immediately after the collision, the y—component of the velocity of the 0.2 kg object is 1 m/s upward. What is the y~component of the velocity of the 0.1 kg object immediately after the collision? 0.5 m/s d. downward 0.5 m/s upward 2 m/s e. downward. 2 m/s c. upward a. 0 m/s b. Free Response ID: A DO NOT WRITE ON THIS PAPER. SHOW YOUR WORK ON THE ANSWER SHEET REPORT ALL ANSWERS TO 3 SIGNIFICANT FEGURES. USE CIENTIFIC NOTATiON WHEN APPROPRIATE {X >100 or X < 0.1} Kzlimvz Ugmmgh W+K0+Ugo+erme+Ugf+Uef+Q UemlakQ—EDY WzFxcosa W=PAt I P=FV L arm-re) Enema FwaN ngmg I? = mi» I, m + no a a + in as :2 FA; :1); 2:31: S a E 1210 +12“.- =v20 + v2r a z 1): sin 62‘ = sin 3b 2 sin (96 I sometimes I” 7- ‘ a b C Given; ax3+bx+c=0 then; xzfliwggfigg c22a2+b2e2abc056 3 YOU MUST DERIVE ANY EQUATION THAT YOU USE THAT IS NOT SHOWN ABOVE. UNLESS OTHERWISE INSTRUCTED: ASSUME FRICTIONLESS, HORIZONTAL MOTION ASSUME ALL SPRINGS ARE INITIALLY AT THEIR RELAXED LENGTH A ZOOO-kg rocket ship is zooming toward Mars when it turns on its engines. The engine’s force pushes the rocket ship towards Mars and varies with time as shown in the graph at right. The rocket engine shuts off at time t m T. rThe rocket increases its speed by 600 m/s. 1 1) At what time T is the rocket engine shut off? 15 40 T A student of mass 50 kg swings on a playground swing, which is very light compared to the student. The student starts her swing from rest, with the bottom of the seat exactly 1.0 m above the iowest point of the motion. The student swings down and, at the lowest point of the motion, grabs a jug of water of mass 4.0 kg. The jug is initially at rest on a smali table right next to the swing, so it does not move vertically as the student grabs it. The student keeps swinging forward while holding the jug, and the seat reaches a maximum height In above the lowest point. Air resistance and friction are negligible. 12) indicate whether in is greater than, Eess than, or equal to 1.0 m. Justify your answer qualitatively, with no equations or calculations. A Z-kg sphere slides east at speed v10 = 5 m/s on a frictionless surface and collides with an 8~kg sphere at rest. After the collision, the 8~kg sphere is moving in the direction [E20°N] and the 2-kg sphere is moving in the direction {E5008}. 13) What is the speed of the 2-kg sphere after the coiiision? F (N) A strange unexplained force F is observed to depend on vertical position as shown in the graph at right. This force acts vertically downward on an object of mass m = 2 kg that is initially at rest at y = it} in. 14) What is the kinetic energy of the object by the time it reaches a vertical position y m l in? A 75—gram bail moving north at 5 m/s strikes a SO—gram ball moving south at 11 m/s. The eoiiision is one—dimensional. 15) If the collision produces no heat, sound or permanent deformation of the balls, what is the velocity of the heavier ball after the collision? l6) What is the maximum. amount of heat that could be produced. by this coliision? A box of mass m = 40 kg is pressed into a spring of force constant k m 5908 N/m at the bottom of a frictionless ramp. k The ramp makes an angle 6= 40“ to the horizontal. The spring is compressed a distance x = 40 cm from its initial equilibrium length, and the box is released from rest. 17‘) How far away from its release position does the box move before it momentarily stops? 18) At what rate is gravity doing work on the box at the final instant the box is moving up the ramp at 2.0 m/s? ...
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