2007 AP PHYSICS B FREE-RESPONSE QUESTIONS R,=2R. Rd=2R :R=R. 3. (15 points) resistance, a closed switch S, and three resistors,

Transcription

1 The circuit above contains a battery with negligible internal each with a resistance of R or 2R. 2 /2 VA VB being greatest. If two (h) (a) resistance, a closed switch S, and three resistors, 3. (15 points) S / 8- R,=2R :R=R /fr Rd=2R 2007 AP PHYSICS B FREE-RESPONSE QUESTIONS (d) Calculate the current in resistor R. (c) Calculate the equivalent resistance of the circuit. For parts (c) through (e), use S = 12 V and R = 200. ii. Justify your answers. 7 resistors have the same voltage across them, give them the same ranking. i. Rank the voltages across the three resistors from greatest to least, with number I -, ii. Justify your answers. A B resistors have the same current, give them the same ranking. i. Rank the currents in the three resistors from greatest to least, with number I being greatest. If two

2 I () I ) 9 6 * :1 1 I 4 4) b

3 V N c1 Al ) I I II 4 ) SI

4 Three Sample Questions 1. Draven, the Glorious Executioner, throws axes at enemies that bounce off them. His axes have a mass of 2.00 kg, and he throws with an initial velocity of 40.0 rn/s along the horizontal. If a target of 150. g is right in front of Draven and is pushed meters away after being hit by an axe, what is the speed of the axe as it bounces off? The coefficient of kinetic friction between the target and the ground is Assume the collision is perfectly elastic and ignore rotational energy. Solution: KEaxe = 1/2mv 2 = l/2(2.00)(40.0) 2 = 1600 J = WfrictiOn = Ffrictlolld = 0.35 * * = 0.35* *(Q, 1 50)(9.80) = 463 J. S Kcef= = 1137J = sqrt(2(1 137)/2) = 33.7 rn/s Ve -Chris/Alex 2. Ekko, the Boy who Shattered Time, hits a time device, which, upon striking the ground, forms a field that slows and stuns opponents. He propels the device at 35 degrees from the horizontal, Given that the device has a mass of 100, grams and travels 100. meters, how much kinetic energy does the device have upon being struck by Ekko s bat? Solution: 0=35 Ax 100. m g9.8m/s m=0.l00 kg I ix*g!(1oo)(9so) = I =3229m/s [Sin (20) sin (70) KE = l/2mv $ 2 = 1/2(0.100 kg) * (32.29)2 = J -Charles 3. Zac, the Zaun Amorphous Combatant, is an elastic ball of goo who can launch himself into the air by acting like a spring. When using his ultimate ability Let s Bounce, he can reach heights of up to 50 meters, despite his immense weight of 300 N on Earth. If

5 x 4 rneters kx x Nrn,k 1875N/rn So, V2kx 2=rngh= l5000nrn The Gravitational Potential Energy at tli apex of Zac s launch should be equal to the Elastic Potential Energy before Zac s launch by the Law of Conservation of Energy. Solution: Zac has a spring constant of 1875 N/rn, how rnuch does he have to contract in rneters to reach a height of 50 rneters? Gravitational Potential Energy = rngh = 300 N x 50 rn = Nrn -Nick

6 Katrina Beske, Andrew Orita, Ayanna Posipanko, Olivia Weng Pd. 7 Kinematics 1. An ice sled powered by a rocket engine starts from rest on a large frozen lake and accelerates at rn/s moves with constant velocity v until t2. The total distance traveled by the sled is 5.30 x 1 o m and the total time is 90.0 s. Findt1, t2, and v. 2. At t1 the rocket engine is shut down and the sled 1t) 0+ irn y.c1-3t(4- sx +x 2 53xo 3, : 3t90t I3t _230t+(1D )D) OjOIO o3j) 2L t 9D-5 r85,3 5A o45 /s t5s 2. A baseball is hit at a 35.0 degree angle above the horizontal and would have a q O-t5 L5 range of meters if nothing obstructs its travel. However, meters away, there is a fence that is 6.00 meters high. Will the baseball clear the fence? If yes, by how much? And if no, where does the baseball hit the fence? 1 k io \Jy2J V tcmc U &i) 1O d 2 oqr - L) c u oso V(u$ cd vi I IJ

7 s_c k M. S A - 1-7<lAt VLt F - ) L v. bf 4 L L u4ty viii L) T 2-t 4 A/i j gondola (the front of the boat) is 40.0 meters away from the bridge. Will Support your answer with numerical evidence. (Assume the boat surface Katrina Beske, Andrew Orita, Ayanna Posipanko, Olivia Weng Pd Mr. Soohoo wants to go back in time to propose to Mrs. Soohoo using physics! He plans a trip to Venice and will propose during a romantic gondola ride. He hires an Italian to drop the ring from a bridge as the gondola passes under it at just the right time so that he can propose. a. The gondola is 7.40 meters in length and is traveling at a speed of 16.0 rn/s on the river. Soon it will pass under a bridge (height above the water = 35.0 meters) where our Italian is waiting with the ring. b. It s time! The ring is dropped (from rest, of course) when the bow of the Mr. Soohoo be able to propose? Will the ring safely land in the gondola? Or will he have to call out an Italian scuba diver to go after the ring? is level with the water). 1 I / r L2 t, -tit t64/ &

8 I V ofballaandballb. f(,ç /.r heading East at 12 rn/s. Ball B is moving West at 8.0 rn/s. Determine the post-collision velocities v 1. Two billiard balls, assumed to have identical mass, collide in a perfectly elastic collision. Ball A is Momentum Problems \J r? 1Vç ri-\ C S2 L) C LZ Is J, J4-1t ice. Determine the magnitude and direction of their post-collision velocity kg skater moving East at 4.33 rn/s. The twokaters entangle and move together across the 3. Two ice skaters collide on the ice. A 39.6-kg skater moving South at 6.21 rn/s collides with a DiD4r) Ir t -E. LL-- I 04 S c I L, k c L4 1Lt 4J U) k-< 4.m Pt I (located behind him). Assuming negligible friction, how much time elapses between when the (,U faf 2. Two children are playing with a large snowball while on ice skates on a frozen pond. The 33-kg child tosses the 5.0-kg snowball at a 28-kg child, imparting a horizontal speed of 5.0 rn/s to it. The 33-kg child is 4.0 meters from the 28-kg child and 8.0 meters from the edge of the pond 28-kg child gets hit by the snowball and when the 33-kg child reaches the edge of the pond? V,c;_ - - k, \Jt v J,, fv,ç L j J ç V1 t 4 1 O 5 e*-4