Course Name

Course ID

Semester

Exam

Applied Physics Department College of Sciences University of Sharjah

Physics (1)

1430115

Fall 2014-2015

Exam 2 Date 11122/2014

Place Time 4:00 pm- 5:00 pm

Instructor kEf '

I Student's name: l1o:

Mark Assigned 12 4 4

Mark Obtained

Please read the folloWing instructions carefully: a) The exam is made up of two parts covering 6 pages:

Part 1: 12 MCQs (one point each)., Part II: 2 Long Answer Questions (4 points each).

c) Calculators are allowed. Sharing Calculators is NOT allowed. d) Indicate your MCQ answers clearly using a pen , c) Mobiles must be turned off and put away!

Version A

I Section:

20

1

Part I Multiple Choice Questions

Q 1- A concrete block is pulled 7. 0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the net work done on the block is 247 J. What angle does the rope make with the horizontal? tJ-=- i g, oj i, D-:: L 1;;)

CY 280 l F 3 3 =~ F ) t-c. 4.2 Nat 162 counterclockwise from F 1 _ C. (.y rJ

~ -~ d. 4.2 N at 108 counterclockwise from F 1

Q6- A I 0. 0 kg mass is placed on a 25 incline and friction keeps it from sliding. The coefficient of static friction in this case is 0.58, and the coefficient of sliding is 0.25. What is the frictional force in this situation?. a. 88.8 N

c:)41.4N c. 46.2 N d. 51.5 N

-

Q7- A Hooke's law spring is compressed I2.0 em from equilibrium and the potential energy stored is 72.0 J. What is the spring constant in this case? a. 7 500 N/m b. 5 000 N/m c. 1 200 N/m

e)ooooN!m Q8- The system shown remains at rest. Each block weighs 20 N. The force of friction on the upper block is:

a. 12 N \J08N

c. 16N d. 20N

-_......:;,

tc_ 1-\J c;, --3 :. \J ( I - ~\.. l) )

H' = 20N a= 3n1 b=4m

Q9- One end of a I. 0 m string is fixed; the other end is attached to a 2. 0 kg stone. The stone swings in a vertical circle, passing the top point at 4 m/s. The tension force of the string at this point is about: v 1-1 '('\('\ ~ L

a. 20N ~ l-: ~-:::. ____. -- ... f .-r- u ~

,...--, - '('("'. (~-~ ) N - (

u b Qll- The potential energy of an object with mass misgiven by (x) = a x 3 - 2 . The X

corresponding force is:

2 b a. -3 ax + 2 3

X

f h-:\- 3 a x 2 - 2 ..!!.... ,~ x3 1 4 1 b

c. --ax 4 2 X

d. -~a x 4 + ~ ~ 4 2 X

Q12- For a block of mass m to slide without friction up the rise of height h shown, it must have a minimum initial kinetic energy of:

a. gh b. mgh/2 c. gh/2

C:)mgh

v Jn

t~ -t D -=-. o -t ~..-. ~ ~ \c-=- ~ 1 ~

4

PART II Long Answer Questions Problem 1: A 0. 2 kg block initially starts with a speed of 6. 0 m/s at point A on the track ABCD as shown in the figure below. The track is frictionless except for the segment BC of length 8. 0 m where the coefficient of kinetic friction flk is equal to 0.35.

I ., -/A-:. . :1 Ill

a. Find the speed of the block at point B.

b. Determine the speed of the block at point C.

I< 17 -t \J c.tk - k c... 1 t.. I ..,.,..\/ t.-

D

20 Ill

--J ,_

vc. t.. =-- v(l, - ;_)A~,~ s: 1 \.... vll> -- jA~ ...._~> ~ ~2- < ~ ::: S'.S ~ J

c.

c. The block continues to slide over the segment CDF till it stops momentarily at the point F. What is the work done by gravity from D to F?.

-:::. t:>K ::. 0-;.-/., O. lf..S.S L

l;

d. Find the maximum height H reached by the block.

Ec ~ Ef

(j) I t... 2 ~ vc 1 0 -.:.Dt~~Y\ -=-) "- S . ) t--\-\ - v c..

--

-

-.lo !._ ,..1,1~-.

Problem 2:

As shown in the figure, blocks of masses mass m1= 10.0 kg and m2 = 2.0 kg are attached by massless string over a frictionless and massless pulley. The coefficient of kinetic friction between each mass and the surface is I-lk =0.30. The angle of the incline is 30 .

a. Draw a free-body diagram for each block.

~ (\""-- ==-' ~ f ----' 1T -4 1t:: 1 I

~ fto l ~t --1 ~ ~ E--~ T'~- ---17 .f, t. ----"\ , -1 \-it \.,}\ 0=) 09 b. Compute the friction force for each block.

t u. - ~"' .,1

-= v~ w, Go.) ~6.!> -= o, 3 )( '\;:) -J. 3. t ~~ ~~ -=--~ f - LA "' ~ J1 \J ~ D.~""" t-f- CJj =- 5~ t t.e. - r 11, t lf t-

c. Determine the acceleration of the system.

d. Find the tension in the string.

--=- t-..,t t11~ t ~ t e - 1-1- 1.41- T S./

v_,_r.l_&_ ... ---~-H~_- +t~ } -....., -t WI L.

~ I o-~. 4. ~ },t, ~~ - ~>. s - > 4 /-t-L

l.'f-f- J.-./rL

6