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1321 Test 1

# 1321 Test 1 - Phys 1321-19166 Spring 2.011 Name SOLU l l 3...

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Unformatted text preview: Phys 1321-19166 __ Spring 2.011 Name: SOLU l l 3 Exam 1 1. (10 pts) A child tries to throw a pebble on the ﬂat roofofa building. The building is 5 m tall and the pebble is released from the child's hand from a height of 1.5 m, at a distance of 4 m away from the building and at an angle 00 = 50° above the horizontal. (a) What is the minimum initial speed required for the pebble to barely reach the roofs edge? (b) If the initial speed is 15 m/s how long is it going to take for the pebble to land on the roof? (c) At what angle with respect to the horizontal will the pebble be moving right before landing? (a) 4 = Vocmaot (4) 9: GS HID/5114001 ~312 (a) . z 6:“ 4-5—4’l‘3/ylmbo4t ~4,ﬁt2(=> <=> trail—(lsmgfﬁ +35 =0 {7. : 44‘461+\l4l.4az—m.6 2 Laggs 6‘3 (q 0“ gfa AAA/g '- 45 C0330 _ 4 __ Vocmﬁo — ‘ .x=\/ VOA£M§0 _ \l 5 .37: gg " 50 4.3 ’- V3 \Mgoo—Cﬁ‘g) 4 m V»: W8 :— ~__a Vx “jrﬂQ/w/s 6 : tat/«4 <._ => 2. (10 pts) A truck of mass 2 tons accelerates up a road inclined at l0° with a 1-ton trailer in tow. If the truck's acceleration is a =l.8m/s2, find (a) the tension in the towing cable and (b) the friction force between the truck's wheels and road. Neglect any aerodynamic forces as well as the rolling resistance of the wheels. T F. 7 1 f— — ‘ 1 G l‘mck: l’f --l-/1M.3LAmiaz/M'OK l ___ 4° VG; ‘ ‘ 0 Trailer; 1—”sz W9 :Mlq E} -(M,+mz)g,/M&:(M,+mz ck @) T = M2 (a-l‘i A£M8>=4000<4q y+ﬂ‘g IM‘M '003: = 3502M ~11— 35 MN a“ =<W.+We)(a+galmﬁ)=3000(4‘g+g'g/X(M40<>: 1" 40,50‘2’N’5- 40.9 IAN 3. (10 pts) A 6 kg hawk dives at a constant speed of 40 m/s to catch a prairie dog. Right before the capture the hawk's direction of motion is horizontal and the instantaneous radius of curvature of its trajectory is p = 200m. After catching the prairie dog, the hawk ﬁnds that maintaining the same airspeed and the same attitude with respect to the airﬂow (ACL =const.) only allows it to ﬂy in a straight horizontal line. (a) What is the hawk's centripetal acceleration right before the capture? (b) What is the lift force generated by its wings at that moment? (c) What is the prairie dog's mass? 2M —é‘= 3K Q1. (5 pts) What is the acceleration at the highest point ofa projectile's trajectory? -—> A ’\ Q2. (5 pts) When a car climbs an inclined road, the total normal force between its wheels and road is (a) greater than its weight less than its weight c) equal to its weight Q3. (5 pts) At the moment a car passes over the top of an arched bridge, the total normal force between its wheels and road is (a) greater than its weight less than its weight (c) equal to its weight Q4. (5 pts) Look at the picture below. Which way does the friction force act on the block that is on the incline? 1W! ragomoucss 0:1, WW M {S 2k} (3/1, MAJC. Q5. (5 pts) A 30 kg crate sits on a horizontal ﬂoor. The friction coefficient between them is Ms = “K = 0.5. (a) What is the magnitude of the friction force if you push the crate horizontally with a force of 100N? (b) What will the magnitude of the friction force be ifyou double the force by which you push the crate? :9: .r .4. ll 3 C) Z 2(— g (3 Q6. (5 pts) A racecar is driven too fast along a curve and starts to skid. Assume that ,uK < us. At the moment when the skid begins, the friction force between wheels and road (a) changes direction but its magnitude remains constant (b) remains unchanged (c) decreases in magnitude but its direction remains the same d increases in magnitude but its direction remains the same @oecreases in magnitude and changes direction by as much as 90° ...
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1321 Test 1 - Phys 1321-19166 Spring 2.011 Name SOLU l l 3...

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