Kuwait University Physics Department

Physics 101

Fall Semester 2nd Midterm Exam

Saturday, Nov 21, 2015 2:00 – 4:00 p.m.

Student’s Name: ………………..………………….…………………………………….…………

Student’s Number: ….…………………………………… Section: ……………………

Choose your Instructor’s Name:

Prof. Fikry El-Akkad Prof. Yacoub Makdisi Dr. Hasan Raafat Dr. Ahmed Al-Jassar

Dr. Abdul Khaleq Dr. Abdul Mohsen Dr. Tareq Al Refai Dr. Belal Salameh

Dr. Fatema Al Dosari

Dr. Nasser Demir

Grades:

# Q1 Q2 Q3 Q4 Q5 SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 LP1 LP2 Total

Pts

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 20

Important:

1. Answer all questions and problems. 2. Full mark = 20 points as arranged in the above table.

i. 5 Questions ii. 11 Short Problems

iii. 2 Long Problems. 3. No solution = no points. 4. Use SI units. 5. Check the correct answer for each question. 6. Assume g = 10 m/s2. 7. Mobiles are strictly prohibited during the exam. 8. Programmable calculators, which can store equations, are not allowed. 9. Please write down your final answer in the box shown in each problem. 10. Cheating accidents will be processed according to the university rules.

GOOD LUCK

For Instructors use only

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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Part I: Questions (Choose the correct answer, one point each)

Q1. You stand on a bathroom scale on the floor of an elevator. The scale shows the maximum reading

when the elevator:

* moves downward with increasing speed

* moves downward with decreasing speed

* remains stationary

* moves upward with decreasing speed

* moves upward at constant speed

Q2. A ball of mass m is thrown from point A off a cliff of height h with an initial speed vA and strikes

the ground with speed vB at point B. Neglecting air resistance, the change in total mechanical

energy of the ball from point A to point B is

* Zero

* mgh

* –mgh

* ½ mvB-½ mvA

* ½ mvB2-½ mvA

2

Q3. A block of mass m1 rests on a block of mass m2 and the combination rests on a table as shown in the

figure. The force exerted on m2 by the table equals:

* m g * m m g * m m g * m m g * Zero

Q4. Three masses A, B, and C are connected by a system of massless pulleys and light strings and

move as shown in the figure. The work done by the force of gravity on masses A, B, and C

respectively is

* positive, positive, negative

* zero, positive, positive

* zero, positive, negative

* zero, negative, negative

* zero, negative, positive

Q5. A pendulum moves along the trajectory as shown in the figure. At point B in the figure, the

tension in the string and the kinetic energy, respectively are:

(Neglect air resistance)

* maximum, minimum. * minimum., minimum. * minimum, maximum. * maximum, maximum. * Tension and kinetic energy are constant throughout the motion.

 

 

h

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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Part II: Short Problems (1 point each)

SP1. The only two forces acting on a 5 kg object are F 5ı 17ȷ N and F 15ı 33ȷ N . Calculate the

acceleration (in m/s2) of the object in unit vectors notation.

Σ

4 10 /

SP2. A horizontal force Fx acting on a particle varies with the position as shown in the graph below.

Find the work (in J) done on the particle as it moves from x=0 m to x=6 m.

3 30 1 10 2 10

20J

SP3. A coin placed 0.5 m from the center of a rotating horizontal turntable slips when its speed is

1.5 m/s. Calculate the coefficient of static friction between the coin and the turntable.

.

.0.45

SP4. A constant force 4 3 acts on a particle, if the displacement of the particle is

Δ 8 6 calculate.

a. the work (in J) done by the force.

b. the angle between the force and the displacement.

a. . Δ 32J

b. .

| | √ √130°

 

Answer: 4 10 /

Answer: 20J

Answer: 0.45

Answer: 130 °

Answer: 32 J

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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SP5. A crate is pushed at constant speed up a rough incline by a horizontal force F as shown in the

figure. If the crate moves up the incline, draw the free body diagram of the crate.

SP6. A particle of mass 0.8 kg is under the influence of a conservative force whose potential energy is

U(x)= 6x2-20x, where x is measured in m and U is measured in J. Find the acceleration (in m/s2)

of the particle at x=2.0 m.

12 20

2 12 2 20 4

.

5 /

SP7. A pilot of mass m = 60kg in a jet aircraft executes a loop-the-loop, as shown in the figure.

The aircraft moves in a vertical circle of radius 800 m at a constant speed of 200 m/s. Determine

the force (in N) exerted by the seat on the pilot at the top of the loop.

60 10

2400

SP8. A man pushes horizontally on a 100 kg crate and moves it at constant speed of 1.5 m/s on a

rough horizontal surface, as shown in the figure. If the coefficient of kinetic friction between

the crate and surface is µK = 0.40, find the power (in watts) delivered by the man.

0.4 100 10 400

600

Answer: 5 /

           

 

n

fk mg cos θ

F sin θmg sin θ

Answer: 2400

Answer: 600

mg n

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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SP9. A 15 kg object rotates in a horizontal circle of radius 12 m. If its speed increases at a rate of

0.8 m/s2, calculate the magnitude of the horizontal components of the net force (in N) acting

on the object at the instant when its speed is 3 m/s.

0.75 /

0.75 0.8 1.097 /

16.5

SP10. A 4 kg block is projected from the top of a frictionless incline toward a spring with speed

v = 2.0 m/s as shown in the figure. If the spring is compressed a distance of x=0.2 m when the

block momentarily stops, find the spring constant k (in N/m).

Σ Δ

sin 0

4 10 3 sin 30 0.2 4 2

60 0.02 8

3400 /

SP11. In the shown figure, the block m1=9 kg rests on a rough horizontal surface. If we begin to

increase m2 so that it begins moving downward when it reaches 4.5 kg, calculate the coefficient

of static friction between m1 and the surface.

0 0 0

. 0.5

Answer: 16.5

Answer: 3400 /

Answer: 0.5

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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Part III: Long Problems

LP1. A box of mass m1=4 kg on a frictionless inclined plane is connected by a lightweight cord to a

box of mass m2= 8 kg on a horizontal rough surface (µk= 0.2). If a force (F= 60 N) is applied to

m2 as shown and it moved to the left.

a) Calculate the magnitude of the acceleration (in m/s2) of the system. (1.5 points) sin

sin

°

. °

2 /

b) Calculate the tension (in N) in the cord. (0.5 point)

sin

sin 4 10 4 2

28

Answer: 2 /

Answer: 28

 

Kuwait University – Science College – Physics dept. – PHYS 101                                                                               Fall 2015/2016 (November 21, 2015) 

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LP2. A 0.5 kg block initially compresses a spring of force constant k= 2000 N/m a distance of x=0.2 m

before being released from rest at point A. The block then slides along a smooth track until point

B, then rough between points B and C. If the radius of the curved part of the track is R=2.0 m.

(a) Find the magnitude of the normal force (in N) on the block at point B.

(1.5 points)

2 2000 0.2 2 0.5 10 3.6 44

cos 37°

cos 37° 22 4 18

(b) If the block’s speed at point C is 6 m/s, find the work done (in J) by friction on the block

between points B and C. (0.5 point)

2

0.5 6 0.5 10 4 2000 0.2

9 20 40

11J

yB = 3.6 m

Answer: 18

Answer: 11 J

B

37 mg cos 37

C