Phys121 M1 2011_Soln

Phys121 M1 2011_Soln - Pity; ill/Pilgrims“ /Zoii...

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Unformatted text preview: Pity; ill/Pilgrims“ /Zoii Conceptuals Q (circle one) A mass is seen to move in a straight line at constant velocity. Therefore, there are no forces acting on it. . F 7 7 _ m . TRUE ALSE 4—3-2” -[/' i "—43 '7 ' 5 V, R 2 FL 2:) Go as 7L V _C_2 (circle one) Two bullets are fired simultaneously parallel to a horizontal plane. The Faffti/{f bullets have different masses and different initial velocities. Which one will strike the. plane first? A) the fastest one C) strike plane at same time. -, For anj war: if? _ grimlyji D) the lightest one - e I (a a6 a. :2, E) the heav1est one _ a? I 1 Mar k5, _ have 94”? éf Q; A boy stands on a scale in an elevator. His feet are stuck to the scale by Velcro so the feet and the scale are always in contact (the Velcro by itself does not create new forces). The scale has springs in it so that when they are compressed, they push against the boy. Thus, when the elevator is sitting still on the surface of the Earth, the scale reads SOON for the SOKg boy (for gganh=10). We call a reading on the scale the boy’s “apparent weight.” For each of the below, state whether the boy’s apparent weight will he more than SOON, less than SOON, zero, or insufficient info i. the elevator is sitting still on the surface of the Moon (gmoon = (l/6)gganh) 2. the elevator is accelerating up and away from the Earth but very far from the Earth surface in outer space 3. the elevator is accelerating up and away from the Earth but near the Earth surface 4. the elevator was hanging above the Earth and someone cut the cord so it is now plummeting to Earth - no air drag Problem 1 Last Name: Two blocks are at rest on a frictionless incline, as shown in the figure. at are the tensions in the two strings i 11166.3]. : kg and m2=4.2 kg? Problem 2 Last Name: ' ion between them. The Ws'applied to the 10 Kg A 10 Kg wooden block sits on a 30 Kg wooden bloc 30 Kg block is sitting on ice (no friction). A force block, as shown. 1. Find the force of friction between the 2 bloc s if there is no slippage between them. i: DON 2. Find the acceleration of the blocks. - gut/Lgfi‘fuh? F-3cM :[04 Problem 3 Last Name: Three blocks, connecting ropes, and alight frictionless pulley comprise a system, as shown. An external force P is applied downward on block A. The system accelerate . ' ' the rate of 2.5 m/sz. The tension in the rope connecting block B and block C equal N In the figure above, the external force P is closest to: A)170N C)210N D) 230N E) 250 N Problem 4 Last Name: John is at the beach. He throws a light plastic ball with an initial speed of 2 m/s horizontally directly against the wind. The wind is blowing horizontally towards John and continually exerts a constant force F =- 0.02N pointing towards John. The wind is so strong that theforce of gravity plays no role in the motion of the plastic ball. (The mass of the ball is 20 gm.) 1. How long does it take for the hall to come back to John from after it leaves his arm? {mfg L’IXW I‘m! 2. What is the maximum distance .H _ the ball gets to away from John? “gm/3 i'wdfi :- 0' E {_..__ Z ,1;@---~*-‘"" if“ 91/4 5K 6: - W i rid Paul now stands 2m away from John to his right and perpendicular to the wind. John now throws the plastic ball at an angle 8 to the wind (with the same initiai speed). 3. What angle must he choose so that the plastic ball exactly hits Paul? I! f/ I J a . '8 f ’11 Ev Frame LL pm” S“ 77% m- @4 ‘ at“? Ugh to [To rat was wig; BLANK PAGE (one more problem on next page) @ at? 2'9 50mg+flu€c€l ve—fii'btotfi/MS“ Problem 5 Last Name: Etc“ . . . . 1’ A 2.0 '7 wood block IS launched up a wooden ramp that IS inclmed at a 35 angle. The Witt. . . . . . . . block’s initial speed is 10 “if Q. There is kinetic frictlon, ttk : 0.2. Static friction IS not important here. W W W flué/mcg (a) What #enicaLhnghtmdoes the block reach above its starting point? (b) What speed does the block have when it slides back down to its starting point? m4: waft/Pig "/mfliélflfg Z AX (/7fi 2‘: 2ngX flf’gflf ...
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Phys121 M1 2011_Soln - Pity; ill/Pilgrims“ /Zoii...

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