Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
Spring Semester, 2015-2016
Monday, May 16, 2016
11:00 a.m – 1:00 p.m.
Student’s Name: ………………..………………….………………
Student’s ID Number: ….……………………………………….. Section: ……….……….……
Instructors : Drs. Al-Refae, Davis, Kokaj, Rakhshani and Razee
Instructions to the Students :

Answer all the questions

Show all your working

All communication devices must be switched off and placed in your bag.
Anyone found using a communication device will be disqualified

Programmable calculators, which can store equations, are not allowed.
 Take g = 9.8 m/s 2 .
For use by Instructors only
Prob.
Marks
1 2 3 4 5 6 7 8 9 10 Total

Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
1. A car travelling at a speed of 72 km/h suddenly accelerates at a rate of 2.5 m/s
2
over a distance of
280 m. How much time it takes the car to travel these 280 m? ( 4 points)
2. Two boxes of mass M
1
and M
2
are joined by a string which passes over a pulley. The box of mass
M
1
= 6 kg is on an inclined plane of θ = 40 ̊ and with coefficient of kinetic friction µ k
= 0.15 between the box and the surface. When released, the box M
1
moves down the incline with acceleration a
= 0.5 m/s
2
. ( 4 points)
(a) Find the tension F
T
in the string joining the two boxes.
(b) Find the mass M
2
.
For M
1
For M
2

Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
3. A box of mass M = 8 kg is being pushed by a horizontal force of magnitude F on a rough surface with coefficient of kinetic friction µ k
= 0.03. The box attains an acceleration of a
= 0.2 m/s
2
. If the box is pushed continuously for 15 s, how much work is done by F ? ( 4 points)
4. A ball of mass m = 0.5 kg is dropped on to a fixed vertical spring of stiffness constant k = 600 N/m from a height of d = 90 cm above the spring. By how much the spring will be compressed?
( 4 points) d

Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
5. A wheel of radius r = 50 cm starts off from rest and rotates with constant angular acceleration α.
At t = 4 s, the wheel reaches 40 rpm.
(a) What is the tangential acceleration a tan of a point P on
( 4 points) the edge of the wheel?
(b) What is the radial acceleration of the point P at t = 3 s? a . b . b.
6. An object is formed by bending a thin and uniform rod of length 16 cm to three segments 1, 2, and 3
as shown. ( 4 points)
(a) Write down the x and y coordinates of the center of mass of each segment.
(b) Find the y coordinate of the center of mass of the object. y
(use the coordinate system given in the figure)
2
1 3 4 cm x a.
8 cm

Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
7. The figure shows a beam of mass m = 30 kg and length L which is supported by a cable to remain horizontal. The three forces applied on the beam are shown. Find the magnitude of force that the wall applies on the beam. ( 5 points)
F
F
T
30 ̊ mg
8. A container is filled with water and oil as shown. Take h
1
= 2m and h
2
= 3m, calculate the gauge pressure at the point P at the bottom of the container. The density of the oil used is 600 kg/m
3
and that for water is 1000 kg/m
3
. ( 3 points)
Oil h
2
P
Water h
1

Kuwait University, Physics Department PHYS 121 Final Exam: Spring 2015-2016
9. The mass M shown in the figure undergoes simple harmonic motion with a frequency of 2.5 Hz.
When a mass m = 0.4 kg is placed on top of M , the oscillation frequency drops to 2.0 Hz. Find the value of mass M and the spring constant k . ( 4 points) k
M
→
10. At a distance of 5 m from a loudspeaker the sound level is 130 dB. ( 4 points)
a. Assuming uniform spherical spreading of the sound and no absorption in the air, calculate the power output of the speaker.
b. How far away from the speaker the sound level would be 90 dB?