NAME (Print)_____________________________________________________________________
Borough of Manhattan Community College
Course Physics 210
Instructor: Dr. Hulan E. Jack Jr.
Date March 31, 2011
Mid Term Exam
INSTRUCTIONS: Do any 6 of the 8 problems below. Check the 6 you want me to grade, otherwise
I grade the first 6 problems
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1. Light travels a distance called 1 lt yr (light year) in a year. The speed of light is c = 3.00x108
m/s. Find the value of a lt yr in m (meters) given the data
1 yr = 365.4 days, 1 day = 24 hr, 1 hr = 60 min,
1min = 60 s.
pseudo code yr -> day -> hr -> min -> s .
(a) Write the program NO NUMBERS YET. (Complete it below.)
d = ct = 3.00 x108m/s *t = 3.00 x108m/s *1 yr (
(12 pts)
)
(b) NOW, fill in the numbers. You can fill them in your program above.
(NO NOT DO THE CALCULATIONS)
(5 pts.)
2. Given the two vectors A and B.
(a) .Sketch R = A+B on the picture.
(b). Explain in words what you did.
(4pts)
(5 pts)
(c). On your resulting diagram , sketch the x and y components of each of the vectors A, B and R.
(8pts)
y
B
A
x
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NAME (Print)_____________________________________________________________________
Borough of Manhattan Community College
Course Physics 210
Instructor: Dr. Hulan E. Jack Jr.
Date March 31, 2011
Mid Term Exam
3. A car of mass mc = 1000 kg travels along a straight flat road with an initial velocity vi = 30.0 m/s.
The tired driver sees that he is about to run into a large fallen
tree, jams on the breaks. Traveling with a constant
acceleration a , for a time t = 5.0 sec the car hits the tree
with a final velocity vf = 5 m/s. Find the acceleration, a, and
displacement, x, of the car during this time.
v
road
tree
the
v (m/s)
(a). What is the acceleration? Definition - symbols (4pts),
numbers
(3 pts).
40
30
20
10
0
(b). What is the displacement during this time ? In symbols (6pts),
numbers
(4pts).
1 2 3 4 5 6
4. Suppose that the above car has acceleration a = -4m/s2. What is the force, F, acting car as it
t (s)
approaches the tree? What is the coefficient of friction, k, for the friction force between the car and
the road?
v
(a). Sketch a Free Body Diagram of the car on the car picture.
Include the acceleration.
(4 pts)
(b). Write down the Laws of Friction
(3 pts)
road
(c). State Newton’s 2nd Law for the car. And fill in the details
Horizontal direction. (+<-)Fh = ma. (3pts)
Vertical direction.
And solve for N
(2pts)
(2pts).
(d). Solve for k. In symbols, a, g, etc. (3pts).
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NAME (Print)_____________________________________________________________________
Borough of Manhattan Community College
Course Physics 210
Instructor: Dr. Hulan E. Jack Jr.
Date March 31, 2011
Mid Term Exam
5. After the car in Prob. 3 comes in contact with the tree, it takes a time t = 0.02
to stop. What average force F acts the car?
(a). What is the linear momentum of the car? Definition (3pts), fill in the
numbers with units (3pts).
(b). State the Physical Principle for this situation. name (2pts). Formula (4pts)
(c). Get the formula for the force F. (4pts) . Fill in the numbers. (1pts).
6. Two objects are connected by a light “tight” string passing over a
light, frictionless pulley as in the figure. The 5.00-kg object is released
from rest at a point 4.00 m above the floor. Use Conservation of
Energy.
(a). Determine the speed of each object when the two pass each other.
Write in terms of the symbols m1, m2, v1i, v2i, h1i, h2i , v1f, v2f,
h1f and h2f . “i” is for initial, and “h” for half way.
( 6 pts)
(b).
h1i =4.00m , h2i =0m ,
h1h = h2h =2.00m WHY? ( 2pts)
v1i = v2i = 0, WHY? ( 2pts)
v1h, = v2h = v WHY? ( 2pts)
(c). Substitute the appropriate numbers
(3 pts)
(d). Get v terms to the left side of the equation (2pts)
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s
tree
NAME (Print)_____________________________________________________________________
Borough of Manhattan Community College
Course Physics 210
Instructor: Dr. Hulan E. Jack Jr.
Date March 31, 2011
Mid Term Exam
7. A space habitat for a long space voyage consists of two cabins each connected by a cable to a central
hub as shown in the figure. The cabins are set spinning with a constant angular velocity  around the
hub axis, which is connected to the rest of the spacecraft to
astronaut
generate artificial gravity.
hub
NOTES: v = r W=mg.
(a) Sketch a Free Body Diagram
of the astronaut, of mass m, lying
on the floor. See picture.
(4 pts)
(b) Write Newton's second
law for the above astronaut in
terms m, velocity v, distance
from the hub r, and the normal
force n.
(5pts)
(c) Find n for when the astronaut
experiences half his normal Earth
weight?
(3pts)
(d) Find the tangential velocity v
in (c) , above.
In Symbols.
(5 pts).
r
cabin
cabin
8. An electric motor rotating a grinding wheel at initial angular speed i =1.00 X 102 rev/min is
switched off. Assume the wheel has a constant angular acceleration  =- 2.00 rad/s2 . Find how much
time, t, to stop and the angular displacement  while stopping.
(a) Convert i to rad/s (4 pts)
(b) Write the definition of angular acceleration  (formula). (2pts)
(c) Solve for the stopping time t. In symbols (formula) ( 4pts), put in numbers (2pts)
(d) Calculate the angular displacement, while stopping.(5pts)
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