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Unformatted text preview: Physics Department
Physics 101 First Midterm Exam Summer 2009 Thursday, July 16th, 2009
6:00 pm. — 7:30 pm. Student’s Number: Choose your Instructor’s Name: Dr. Hala Al—Jassar Dr. Fatma AlDossari
Dr. Adnan AlYaseen Dr. Tareq Alrefae
Dr. Ashraf Zaher Grades: IIIIII. Important: , Answer all questions and problems. Each question will be assigned 1 point. Each problem will be assigned 2 points. No solution = no points. Check the correct answer for each question. Assume g = 10 m/sz. Mobiles and Pagers are not allowed during the exam. Programmable calculators, which can store equations, are not allowed. WHQPPP’P!‘ GOOD LUCK Part I: Questions (Choose the correct answer) 1. A vector of magnitude 20 is added to another vector of magnitude 25. Which of the following can be a valid answer for their sum? (a) Zero.
(b) 3.
(d) 47.
(e) 500. 2. A particle is moving in a straight line, at a constant velocity of 20 m/s. Which of the following ﬁgures re resents its motion? a a a a a
l t 4 I 4 t t l I
(a) (b) (C) (d) (2) Answer (e) as a = 0 3. An object moves at a constant speed in a clockwise
direction around an oval track. The geometrical center
of the track is at point 0. When the object is atpoint P,
which arrow shows the direction of the object’s
acceleration vector? (a) arrow #1 (directly away from point 0)
(b) arrow #2 (perpendicular to the track) (0) arrow #3 (in the direction of motion) /
(d) arrow #4 (directly toward point 0) oval track (e) arrow #5 (perpendicular to the track) Answer (e) as a must be perpendicular to v 4. A canon ball is ﬁred horizontally from the top of a
cliff at a height H as shown in ﬁgure. When the ball
has travelled a distance 0/2, the value of h is: (a) H/IO.
(b) [1/5.
(c) m
(d) H/3.
(e) H/2. Answer (0) as y is proportional to 1‘2 while x is proportional to t 2/4 Part II: Problems (solve the following problems) 1. Vector B , shown in ﬁgure, has a magnitude of ﬁve. If vector —o A =3i+63, ﬁnd the angle that vector R = B—Amakes
with the positive x—axis. A B B = —(5c0530°) E + (551113032 = 41.33 f +2.5} R = B—A =(Bx —Ax)i+(By my); = —7.33€— 3.5} ’3'5 = 180° 4 tan1 3 = 180° +253 = 205.5°
3 7.33 6 = tan1 2. A stone is thrown vertically upward. On its way up, it passes point
A, with speed v, and point B, 3.75 In higher than A, with speed v/2. Calculate the value of the speed v in m/s.  §    v/2
02=v§_2g,5y 375m; (0.57))2 = 02 ——2x 10x 3.75 ' 0.2502 = '02 — 75 0.7502275 :> 02:100 :> vzlﬂm/s A 3. A particle, moving along the xaxis, has a position given by x = 2415—2153 , where x is in In,
and t in 5. What is the magnitude of the acceleration when the particle is momentarily at rest? _dx _—=246152
v dt do dzx
=—=—=»12t
'2 dt dtz Nomotiona (0:0) :> 24—6152 =0 :> t=25
a=—1.'2><2=—24crn/s2 => a=24m/s2 3/4 4. A ﬁghter jet, ﬂying horizontally at an altitude
of 500 m, as shown in ﬁgure, drops a shell
when its velocity was v0 = 100 m/s and then
accelerates away at a constant acceleration a.
Find its minimum acceleration such that it will
be at least at a distance d = 1300 m away from the position at which the shell hits the ground. h = l th 2:, 500 2 5t2 2) t = 10 5 Initial position of the jet and the shell
2 Final position of the jet
d1 = not = 100x10 = 1000m d2 = de ——h2 = #13002 45002 = 1200 m 011 +al2 = vattéatz :> 2200 = 1000+50a => a = 24 m/ 52
Final position of the Shel! 5. It is required to design a Ferris wheel, at an amusement
park, such that it makes 6 revolutions per minute, while
moving at a constant speed v = 3.14 m/s. Find the radius,
R, of the Ferris wheel. T=Q=1OS
6 v=27rR :> R=ﬂ2> R=3'14X1025m
T 2% 27: 6. A man revving a boat, at a constant velocity of 5 m/s
relative to the water, makes a round trip from point A to
B in the water, as shown in ﬁgure. The time taken to
ﬁnish his round trip in the water is 15 s more than the
time taken to make the same round trip on land when
running at a constant velocity of 4 m/s relative to earth.
Find the speed of the water, chmm, relative to earth. its 2 2x120 zy 2605
4 4
arm, = am +15 = 60+15 = 75 s
gunﬁghﬂjiﬂzﬂ
5 + vcurrent 5 F— vcurrent 25 _ Umrrent
25—vcurrent = 16 Z} vmrrent = 3 m/S 4/4 ...
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