# Midterm

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```					  CSULA                           MIDTERM EXAM I                       PHYSICS 211
Fall 2006
Professor: Rafael Obregon

Name (Last, First): _________________________________________

1. PLEASE show all work, writing the essential steps in the problem solution, do not
just write the answers. Write appropriate formulas first (if you can, put in numbers).
Partial credit will be GIVEN, provided that essential work is shown. Organized,
logical, easy to follow work will receive more credit than disorganized, no logic
and/or inadequate work (e.g. missing units).
2. PLEASE write neatly. Before handing in your solutions: a) number the pages and
put the pages in numerical order, b) keep the problem solutions in numerical order,
expect me to give it the credit it deserves.
3. This exam, pen or pencil, eraser, Help Sheet provided by me and calculator (no
sharing) are the only things allowed on your desk.
GOOD LUCK!!!

Problem             Points
No. I (25 pts)
No. II (75 pts)                                    GRADE: _____________
TOTAL (100 pts)
I)   CONCEPTUAL QUESTIONS (5 points ea): Answer these in a few complete and
grammatically correct English sentences. Note that a correct explanation will be worth 4
points and merely choosing the correct answer will be worth 1 point.

1. A rock is dropped at the same instant that a ball, at the same initial height, is
thrown horizontally. Which will hit the ground first? Explain (briefly!) your answer.

2. Two vectors have unequal magnitudes. Can their sum be zero? YES or NO.

3. A student at the top of a building of height h throws one ball upward with a speed
of vi and then throws a second ball downward with the same initial velocity vi .
Which ball will have the greater speed when it reaches the ground?

4. A particle moves in a circular path of radius r with speed v. If its speed increases to v/2
while traveling the same circular path, then the centripetal acceleration of the particle
has changed by a factor of: (a) 1/4, (b) 1/2, (c) 2, (d) 4.

5. If you push on a heavy box that is at rest, you must exert some force to starts its
motion. However, once the box is sliding, to maintain that motion you can apply:
(a) a smaller force, (b) a large force, (c) an equal force, (d) zero force.

II) Solve the following problems (15 points ea)

1. A projectile is fired in such way that its Horizontal Range (R) is equal to TWO times its
Maximum Height (h). What is the Angle of Projection ().

2. A car accelerates from rest at constant acceleration 2.00 m/s2 when it is crossing a 30.0
m wide intersection.
A) (8 points) How long does it take the car to cross the intersection?
B) (7 points) What is its final velocity at the end of the intersection?

3. A displacement vector D lying in the xy plane has a magnitude of 50.0m and a direction
of 210o respect to the positive x-axis.
A) Draw a sketch of the vector displacement D.
B) Find the rectangular components of the vector. (Don’t forget the units)
C) Write the displacement vector D using unit vectors. (Don’t forget the units)
4. When two objects of unequal mass are hung vertically over a frictionless pulley of
negligible mass, as the figure, the arrangement is called Atwood Machine.
A) (2 points) Draw a free-body diagram for each mass.
B) (4 points) Applying Newton’s 2nd Law, write the equation of motion for y-direction
for each mass.
C) (4 points) Determine the magnitude of the acceleration (a).
D) (5 points) Determine the tension (T) in the light cord.

5. A car is traveling with speed v around a curve of radius R as shown in the figure:
A) Find values of the components of the normal force n (nx and ny)
B) Using Newton’s 2nd Law write equations of motion for x and y direction.
C) Finally, derive a formula for the angle () at which the road should banked so that
no friction is required.

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