Download 1 - EMU Physics Department

EASTERN MEDITERRANEAN UNIVERSITY - Department of Physics
PHYS 101 –MIDTERM EXAM
2008-09 SUMMER SCHOOL (August 05, 2009)
STUDENT NO
NAME
SURNAME
BOOKLET
A
INSTRUCTIONS
 Answer all the questions.
o Section I consists of 15 multiple choice questions. Each question is worth 1 point. Mark the
correct answers on the ANSWER GRID below, by encircling the appropriate letter.
o Section II consists of 3 problems worth a total of 15 points. Write your answers directly on
the page of each problem. For full credit, fully justify your answers.
 Time allowed for the exam is 120 minutes.
 You may NOT use books, notes, dictionaries, formula sheets, PDAs, mobile phones, etc.
 You may use a calculator.
CONSTANTS AND USEFUL FORMULAS
Constants
g = 9.80 m/s2
G  6.67  10
11
2
Nm / kg
Velocity and acceleration:
dr (t )
dv (t )
v(t ) 
, a(t ) 
dt
dt
Radial or centripetal acceleration:
2
Constant acceleration kinematic equations:
1
v(t )  vo  at , r (t )  ro  v ot  at 2
2
v2
aR  ac 
r
Newton’s law of universal gravitation:
mM
F G 2 ,
r
Newton’s second law:
Mass of the Earth= 5.9742 × 1024 kg
Mass of the Moon = 7.36 × 1022 kg
Wnet  K 2  K1
1
K  mv2
2
 F  ma
The average centre-to-centre distance from
the Earth to the Moon is 384,403 km
ANSWER GRID
Mark your answers to the test
questions on this grid by
PLACING A CIRCLE around
the letter of your choice.
Force of friction:
Ffr  Fk  k FN (kinetic)
Ffr  Fs   s FN (static)
 
W  F d
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This line for instructor use only
Section I
For
(15
points)
instructor
use only
Problem 1
( 5 points)
Section II (15 points)
Problem 2
Problem 3
(5 points)
(5 points)
TOTAL
PHYS101
Midterm Examination
Summer 2008-09
1. You drive for 30 seconds at 30 m/s and then for
another 30 seconds at 50 m/s. What is your average
speed for the whole trip?
a)
b)
c)
d)
e)
x
(m
)
40 m/s
35 m/s
45 m/s
20 m/s
60 m/s
t
a)
b)
c)
d)
2. You run 20 meters at 10 m/s and then walk 40 meters
at 5 m/s. What is your average speed for the whole 60
meters?
a)
b)
c)
d)
e)
v>0, a>0
v>0, a<0
v<0, a>0
v<0, a<0
7. For a cannon on Earth, the cannonball would follow
path (b). If the cannon was fired on Moon where gMoon
= 0.3gEarth, which path would the cannonball take in
the same situation?
7.5 m/s
15.0 m/s
6.0 m/s
8.0 m/s
10.0 m/s
a)
3. If the average velocity is non-zero over some time
interval, does this mean that the instantaneous
velocity is never zero during the same interval?
a)
b)
c)
d)
a)
b)
c)
d)
e)
they are perpendicular to each other
they are parallel and in the same direction
they are parallel but in the opposite direction
they are at 45° to each other
they can be at any angle to each other
9. You drop a package from a plane flying at constant
speed in a straight line. Without air resistance, the
package will?
Alice’s ball
it depends on how hard the ball was thrown
neither - they both have the same acceleration
Bill’s ball
a)
b)
c)
d)
5. You drop a rock off a bridge. When the rock has
fallen 4 m, you drop a second rock. As the two rocks
continue to fall, what happens to their separation?
a)
b)
c)
d)
d)
8. Given that A + B = C, and that lAl + lBl = lCl , how
are vectors A and B oriented with respect to each
other?
yes
no
it depends
Impossible to tell
4. Alice and Bill are at the top of a building. Alice
throws her ball downward. Bill simply drops his ball.
Which ball has the greater acceleration just after
release?
a)
b)
c)
d)
c)
b)
quickly lag behind the plane while falling
remain vertically under the plane while falling
move ahead of the plane while falling
not fall at all
10. A projectile is launched from the ground at an angle
of 30 . At what point in its trajectory does this
projectile have the least speed?
the separation increases as they fall
the separation stays constant at 4 m
the separation decreases as they fall
it is impossible to answer without more
information
e)
f)
g)
h)
i)
6. The graph of position versus time for a car is given
below. Which of the following statements about the
acceleration and velocity of the car is correct?
just after it is launched
at the highest point in its flight
just before it hits the ground
halfway between the ground and the highest point
speed is always constant
11. From rest, we step on the gas of our Ferrari, providing
a force F for 4 seconds, speeding it up to a final speed
2
PHYS101
Midterm Examination
v. If the applied force were only 1/2 F, how long
would it have to be applied to reach the same final
speed?
e) both the same (N = 0)
14. If you push with force F on either the heavy box ( M2)
or the light box (M1), in which of the two cases below
is the contact force between the two boxes larger?
a) 16 s
b) 8 s
c) 4 s
d) 2 s
e) 1 s
12. A block of mass m rests on the floor of an elevator
that is accelerating upward. What is the relationship
between the force due to gravity and the normal force
on the block?
f)
g)
h)
i)
j)
a) If we push M1
b) If we push M2
c) both are the same
M1
F
F
M2
1
1
2
15. Two blocks of masses 2m and m are in contact on a
horizontal frictionless surface. If a force F is applied
to mass 2m, what is the force on mass m ?
N > mg
N = mg
N < mg (but not zero)
N = 0
depends on the size of the elevator
A
A
B
both the same (N = mg)
both the same (0 < N < mg)
M2
M1
1
F
13. Consider two identical blocks, one resting on a flat
surface and the other resting on an incline. For which
case is the normal force greater?
a)
b)
c)
d)
Summer 2008-09
a)
b)
c)
d)
e)
B
2m
m
2F
F
1/2 F
1/3 F
1/4 F
SECTION II
Problem 1 (total of 5 points)
Box A, of mass mA=10 kg, is placed on a surface inclined at 37° to the horizontal. It is connected by a
lightweight cord, which passes over a massless and frictionless pulley, to a second box B, which hangs freely
as shown. If the coefficient of kinetic friction is 0.20 and mB=20 kg:
a)
Plot the free body diagrams for mA and mB separately. (2 points)
b)
If mA moves to the left find the acceleration of the system? (3 point)
3
PHYS101
Midterm Examination
Problem 2 (total of 5 points)
Use the information given on the cover page to calculate at what
speed does the moon orbit the earth?
Problem 3 (total of 5 points)
A car traveling 60 km/h can brake to a stop
within a distance d of 20 m. If the car is
going twice as fast, 120 km/h, what is its
stopping distance? Assume the maximum
braking force is approximately independent
of speed.
4
Summer 2008-09