Physics Department
Physics 101
Final Exam
Summer Semester 2013-2014
Monday, July 14, 2014
12:00 – 2:00 p.m.
Student’s Name: ………… …….…………………………………….…………
Student’s Number: ….……………………………………
Section: ……………………
Choose your Instructor’s Name:
Prof. Fikry El-Akkad
Dr. Abdul-Mohsen Ali
Dr. Yacoub Makdisi
Dr. Tareq Alrefai
Dr. Hala Al- Jassar
Dr. Fatema Al-Dousari
Dr. Belal Salameh
Grades:
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
points
#
points
Important:
1.
2.
3.
4.
5.
6.
7.
Answer all questions and problems.
Each question/problem will be assigned 1 point.
No solution = no points.
Check the correct answer for each question.
Assume g = 10 m/s2.
Mobiles and pagers are not allowed during the exam.
Programmable calculators, which can store equations, are not allowed.
GOOD LUCK
Kuwait University – Science College – Physics dept. – PHYS 101
Summer 2014 (July 14, 2014)
Part I (Questions): Select the correct answer.
1. Ahmed projects a stone horizontally from the top of a mountain. At the same instant Bader
releases a similar stone from rest at the same height. Which of the following statements is
correct?
a) Ahmed’s stone reaches the ground first
b) Badr’s stone reaches the ground first
Vertically, both stones are in
a state of free fall with zero
initial speed.
c) Both stones reach the ground at the same time
d) Both stones have the same initial velocity
e) No enough information
2. Which of the following free-body-diagrams represents the car going uphill at a constant
acceleration (as illustrated in the figure)?
3. A 2 kg rock is released from rest at a height of 20 m above the ground and feels no air
resistance. What is its mechanical energy at a height of 8 m if the reference coordinates are
taken at the ground level?
a)
b)
c)
d)
e)
320 J
400 J
180 J
Zero
160 J
E = mgh = 2(10)20= 400 J
4. A bowling ball and a ping-pong ball are moving towards you each with the same momentum.
If you exert the same force to stop each one. which of the following statement is correct?
a) The stopping time of the bowling ball is larger
b) The stopping time of the ping-pong ball is larger
J = pf – pi = - ∆
c) Both require the same stopping time
∆ = = Constant
d) Both will have the same stopping distance
e) Need more information
5. The figure shows four identical masses placed at equal distance from the x-axis and y-axis.
Which axis of rotation will yield the maximum moment of inertia?
a) Axis x
b) Axis y
c) Axis a
d) Axis b
e) Axis z (inward through O).
a
y
b
Iz = Ix + Iy
O
x
Kuwait University – Science College – Physics dept. – PHYS 101
Summer 2014 (July 14, 2014)
Part II (Problems): Solve the following problems, and then write the final answer for each
problem in the designated box.
6. Given the vector A = 4 ̂ + 3 ̂ – 2 . Find the angle (in degrees) that this vector makes with
the positive z- axis
= = √
= 111.8̊ ≃ 112̊
Answer:
112 ̊
7. A bullet is fired with initial speed of 150 m/s at an angle of 60o above the ground. Find the x
component of its velocity (in m/s) after 8 seconds from being fired (neglect air resistance).
$% = $& cos Answer:
= 150 cos 60 = 75./
75 m/s
8. Due to air resistance, a 60- kg parachutist experiences an acceleration of 3.0 m/s2 while
falling in the air. If she falls 80 m in 12 seconds what is her final speed (in m/s)?
0 = $ − 2 −80 = $3124 − 3−343124
$ = 24.7 ≃ 25./
Answer:
25 m/s
9. A 2.0 kg block is placed on a rough incline (θ = 20 ̊ ) with friction coefficients µs = 0.60 and
µk = 0.30. Find the frictional force (in N) acting on the block.
789:% = ;8 .< cos = 0.63243104 cos 37
789:% = 11.3=
Answer:
6.8 N
.< sin = 23104 sin 37
= 6.8 N
@AB.< sin < 789:% , ℎBA78 = 6.8=
20 ̊
Kuwait University – Science College – Physics dept. – PHYS 101
Summer 2014 (July 14, 2014)
10. A particle revolves in a circle of radius 0.8 m and makes 12 revolutions per minute (rpm).
Find the magnitude of its radial acceleration (in m/s2).
$ = 2FG7 = 233.14430.84 H K = 1./
IJ
2L =
M
L
=
J.N
= 1.25./ Answer:
1.25 m/s2
11. A 2.0-kg block slides down a frictionless incline while a force F is opposing its motion
causing it to move with constant speed a distance of 5.0 m. Find the work done by F (in J).
OPQR = ∆S
m
.<ℎ + O = 0
F
O = −2310435 sin 374
37 ̊
O = −60U
Answer:
‒ 60 J
12. At t =0, a 0.15-kg particle moving horizontally with velocity -8 m/s is acted upon by a
horizontal force F of magnitude varying with time as shown in the figure. Find the
momentum of the particle at t = 4 ms (in N.s).
2GB2 = VW − VX
Answer:
F(kN)
3243104 + 23104 = VW − 30.1543−84
10
VW = 28.8=Y
0
]_. _`a
2
4
6
t(ms)
13. A block is attached to a spring (k = 500 N/m) on a horizontal frictionless surface. Initially,
the spring is at the relaxed position and the block is at rest. A force of magnitude 100-N is
then applied to the block leading to a compression of the spring. Find the kinetic energy (in
J) of the block when the spring is compressed by 0.20 m.
ZX + O = Z
F
[ = [ + SW
\^ Answer:
]
10 J
SW = 10030.24 − 3500430.24
SW = 10U
Kuwait University – Science College – Physics dept. – PHYS 101
Summer 2014 (July 14, 2014)
14. A 2.0-kg block moving with initial speed of 8.0 m/s on a rough horizontal surface hits a
horizontal spring (k = 500 N/m) and compresses it a maximum distance of 0.40 m. Find the
work done by friction (in J).
ZX + OW = ZW
.$ + OW = [ Answer:
m
OW = 3500430.44 − 324384 = −24U
‒ 24 J
15. A bullet of mass m1 = 0.2-kg is fired into a block of mass m2 =10 kg initially at rest. If the
bullet escapes from the block with only a third of its original speed, while the block acquires
a speed of 8 m/s , find the initial speed of the bullet (in m/s).
. $X = . $W + . $W
0.2$X = 0.2 HK $X + 10384
$X = 600./
Answer:
600 m/s
16. Two identical rods each of length 8m are placed as shown in the figure. Find the distance
between the center of mass of the systems and point O.
d
2b[c9 = b HK ⇒ [fg = 2.
d
2bhc9 = b HK ⇒ hfg = 2.
b
o0, p
2
G = √2 + 2 = 2.83.
O
Answer:
b
o , 0p
2
2.83 m
17. A ball m1 moving east at a speed of 8 m/s undergoes a head-on elastic collision with another
ball m2 moving west with a speed of 6 m/s. If the final speed of ball m1 after collision is
2.0 m/s due west , find the final speed of ball m2 (in m/s).
3$X − $X 4 = −i$W − $ j
k8 − 3−64l = −m−2 − $W n
14 = 2 + $W
$W = 12./
Answer:
12 m/s
m1
m2
Kuwait University – Science College – Physics dept. – PHYS 101
Summer 2014 (July 14, 2014)
18. At t = 0, riders in an amusement park ride are pressed against a wall that revolves with initial
angular velocity ω = 1.60 rad/s in a horizontal circle of radius r = 5.00 m. If the magnitude
of the linear velocity of the passengers increases at a rate of 4 m/s2 find their angular
velocity at t = 5 s.
2 q = rG ⇒ r = G20/ s
t = t& + r
t = 1.6 + 354 = 5.6G20/
s
Answer:
z. {|}~/
19. In the system shown, when the block m ( = 4.0 kg) falls down it pulls the rope causing the
pulley to rotate about a fixed horizontal axis. The block has a speed of 3.0 m/s when it has
fallen 6.0 m. Find the moment of inertia of the pulley (in kg m2), if the pulley has a radius of
0.80 m.
ZX = ZW
.<ℎ = .$ + ut
34
43104364 = 344334 + u 3J.N4
u = 31.6<.
m
6m
Answer:
o
31.6 kg m2
20. A man of mass m = 75 kg lowers himself down from the top of a building by using a rope
wound around a drum as shown in the picture . The drum is a solid cylinder of radius
R = 0.50 m and mass M = 150 kg. Find the angular acceleration of the drum (in rad/s2) at
the instant it starts to rotate.
ICM = ½ MR2 for the drum.
v = ur
.<w = xw r
r=
Answer:
3ys43J4
sJ3J.s4
r = 20G20/ 20 rad/s2