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Unformatted text preview: Sample Midterm Exam # 1
Physics 8A, Spring 2011 (Section 1) Name: Student ID: Discussion Section: Name of Teaching Assistant: This examination has two parts. Part I consists of 11 multiple choice questions worth 4 points each. You need
not show your work here. No partial credit will be given for these questions.
There is no penalty for wrong answers. Part 11 consists of 3 problems. These problems each have multiple parts.
You MUST show your work for these questions. All work must be done in
this booklet. N0 blue books will be accepted. If you need additional paper
for working the problems on this exam, raise your hand and the proctor will
bring you paper. Make sure any additional sheets are stapled to the exam
(the proctor will have a stapler). Calculators are NOT permitted; the arithmetic is designed to be easy. You
may take ONE sheet of 8% X 11 inch paper with equations into this exam
(for the ﬁrst exam, please use only one side of the paper). Please refer to the
fact sheet that has been distributed for information such as the sin and cos of angles. TPerfect Score Score ‘ PART I 44
PART I 1 16
2 15
3 15
TOTAL 90 Part I: (44 points) Answer ALL the questions by writing the letter cor
responding to the best answer next to the question. There is no penalty for wrong answers. 1. The following position vs time graph represents the motion of a toy
car. When does the car have “zero” velocity? 2. Using the same graph as question 1, at which point does the car have
“zero” acceleration? 3. Which of the following is a NOT a unit of acceleration? (a m/s2 ) (b) we (0) J/(mk8;)
(d) kg m /s2 (9) J N /(kg2 m) 4. Consider the vectors fl 2 3+2} an —a best represents the vector 0 = A — 21 d g? = 2—}. Which of the following
? “s
/\ m A
& \Z: " “ l v “j
3 a
X .1
.6": l _ E7 3‘
Auk ‘44.
3 .
d 0/ W
‘2, D
at _ 3‘ 5. A prince is being held captive in a tower which stands 180 m above
the ground. He wraps a distress message around a rock and hurls it
straight down with an initial speed of 25 m/s. After how long does the
message hit the ground? 6. A block of mass 10 kg slides down an inclined plane as shown below. If
the plane makes an angle of 37° with the horizontal and the coefﬁcient
of kinetic friction between the block and the plane is 0.1, what is the
magnitude of the frictional force? ' (a) 5.88 N (b) 7.84 N Z
(c) 9.80 N
(d)
(e) 98.0 N zero 7. A block of mass 10 kg is attached to a spring with spring constant
k = 10 N/m. The spring is stretched 10 cm and let go. What is the maximum velocity the block has? 8. A steel ball of weight W is supported by two strings as shown. Which
one of the following relations must hold? (a)T1—T2:2 . (b) Tlsin6=W (c)T1=W0030 .6“
(d) TE+T§=W v,
(e) T1 sin0=T2 9. A skier of mass 60 kg goes down a slope as shown. If she starts from
rest at the top of the hill, what is her speed at the bottom of the hill.
You may assume there is no friction b 31.3 m/s 500 m (d 242. m/S  o 00 M. .10. A mass is moving clockwise at constant Speed in a circle of radius 10
cm as shown. At t = 0 the velocity is 1 j m/s. The acceleration at t=0isz (a) 10 m/si
(b) —10 m/si
(c) 10 m/sj'
(d) —10 m/sj (e) 5 m/s i+ Sim/33' 11. A mass of 5 kg feels a force F = (4 3 + 3 N. What is the magnitude
of the acceleration the mass feels? Part II 4
You must show the reasoning for your answers. Do this as clearly as possible so that you may be given partial credit if your approach is correct but your
numerical answer is wrong. (Note: A neat easy—toread answer is much more
likely to gain you partial credit than one we can’t decipher!) 1. (15 points) Note: To make the math easier, you may make the approx
imation g =_ 10 m/s.
A boy throws a rock (mass = 2 kg) out a window. The window is 20
m above the ground and the rock has an initial velocity: 17: (53+23)m/s (a) How long does it take for the rock to hit the ground? (b) How far does the rock travel horizontally in that time? (c) What is the ﬁnal speed of the rock? (d) How much work has been done by the force of gravity during the
rock’s total ﬂight? 2‘ (16 points) Masses m1 = 4 kg and m2 = 9 kg are connected by a
massless string that passes over a frictionless pully. m1 is held at rest
on the ﬂoor and m2 is held on a ﬁxed incline of 0 2 45° At time t = 0
the masses are released from rest and start to slide. Mass m2 slides
1.00 m down the incline in 4.0 s. (a) Draw a free—body diagram for each mass (b) Determine the acceleration of each mass (c) What is the coreﬂicient of kinetic friction between m2 and the
incline? (d) What is the tension in the string? 3. (15 points) A pogo stick can be thought. of as a stick with a spring at
the end. (a) Suppose the pogo stick is standing vertically. When a boy (mass:
30 kg) climbs on the stick, the spring compresses 1.0 cm. What is
the spring constant k for the pogo stick? (b) The boy gets off. the stick and this time jurnps on. His initial
velocity when his feet hit the stick is 17 : —10j m/s. How far will
the pogo stick compress? 10 (c) After the spring is compressed in part (b), it begins to expand
again, pushing the boy upward. If the pogo stick transfers all of
its energy to the boy, how high will he go in the air? 11 ...
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This note was uploaded on 04/29/2011 for the course MATH 16B taught by Professor Sarason during the Spring '06 term at Berkeley.
 Spring '06
 Sarason

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