Physics 2414
Midterm #2 – Spring 2005
Version A
Multiple Choice (6 pts each)
1) The masses are at rest and there is no friction. What is the relationship between the
masses and the angles?
a)
b)
c)
d)
e)
m1tan = m2
m1tan = m3
m1cos= m3
m1sin= m3
m1cos = m2
2) Two coins are placed on a rotating platform at the same distance from the center. Coin
A weighs more than Coin B. The coefficient of friction between the coins and platform is
very, very small but nonzero. The platform undergoes angular acceleration, what
happens to coins A and B?
a) Coin A flies off the platform first.
b) Coin B flies off the platform first.
c) Both coins fly off the platform at the same time.
d) Neither coin ever flies off the platform.
e) Not enough information to tell.
3) What is the normal force exerted by a roller coaster track (with radius R)on a car (with
mass M) moving with speed V at the bottom of a vertical loop?
R
a)
b)
c)
d)
e)
Mg
More than Mg
Less than Mg
Less than Mg and exactly zero.
Not enough information to tell.
4) Two satellites (satellite A with mass M and satellite B with mass 2M) orbit about the
Earth with the same radius R. What is the ratio of the periods of the two satellites?
T
a) A  2
TB
T
b) A  1 / 2
TB
T
c) A  1
TB
T
d) A  23 / 2
TB
e)
T
2
T
A
2/3
B
5) A student undergoes a first displacement of 3.6 meters at an angle of 20 degrees
NORTH of EAST. The student undergoes a second displacement of 7.3 meters at an
angle of 40 degrees SOUTH of EAST. The angle of the total displacement is,
a) 15 degrees SOUTH of EAST
b) 62 degrees SOUTH of EAST
c) 21 degrees SOUTH of EAST
d) 62 degrees NORTH of EAST
e) 21 degrees NORTH of EAST
6) A cord passes over two pulleys as shown in the figure. The tension in the cord is 120
N. The magnitude of the force on one pulley by the shaft that supports the pulley is,
a) 60 N
b) 120 N
c) 170 N
d) 180 N
e) 240 N




m
m
7) An object of mass (m) is hanging as shown. What is the tension (T) in the ropes?
m
a) T= mg/(2 sin )
b)
c)
d)
e)
T= mg/sin 
T=mg/cos 
T=mg/(2 cos )
T=mg
8) Two masses are connected by a string which passes over a frictionless, mass less
pulley. One mass hangs vertically and one mass slides on a 30 degrees incline. The
vertically hanging mass is 4.0 kg and the mass on the incline is 6.0 kg. The acceleration
of the 4.0 kg mass is,
a) 0.98 m/s 2
b) 3.92 m/s 2
c) 5.75 m/s 2
d) 6.86 m/s 2
e) 7.84 m/s 2
9) A projectile is projected from the origin with a velocity of 45.0 m/s at an angle of 30
degrees above the horizontal. What is the time it takes for the projectile to hit the ground?
a) 2.29 s
b) 3.02 s
c) 4.59 s
d) 5.31 s
e) 6.04 s
10) A rocket is launched from the origin with an acceleration of 20.0 m/s 2 at an angle of
30 above the horizontal. The launch acceleration lasts for 2.0 seconds at which time the
fuel is exhausted. The rocket then falls with an acceleration of 9.8 m/s 2 downward. What
is the X distance (range) when the rocket hits the ground?
a) 153 m
b) 166 m
c) 187 m
d) 205 m
e) 230 m
11) An object is moving in a circular path of radius R. If the object moves through an
angle of 30 degrees, then the angle is,
a) 0.22 radians
b) 0.52 radians
c) 0.75 radians
d) 1.04 radians
e) 1.75 radians
12) A 4.0 kg mass is moving in a circular path of radius 2.5 m with a constant angular
velocity of 5.0 rad/sec. The centripetal force on the mass is,
a) 250 N
b) 185 N
c) 153 N
d) 107 N
e) 40 N
13) A car of mass m is traveling on a banked curved icy road without sliding. The
velocity of the car is v and the road is banked at an angle of  degrees. The radius of
curvature of the road is r. The normal force is N. What 2 equations do we get using
Newton’s second law?
a) Nsin=0 ; Ncos– mg = mv2/r
b) Nsin=mv2/r ; Ncos-mg=0
c) Ncos=0 ; Nsin-mg=mv2/r
d) Ncos=mv2/r ; Nsin-mg=0
e) Ncosmg=mv2/r ; Nsin-mg=0
14) A boy can swim at 3 m/s in still water. He crosses a 10 m wide river which has a current of
1 m/s. When he arrives at the other side of the river he is straight across from where he started.
How long does it take him to cross the river?
a) 3.33 s
b) 3.54 s
c) 3.00 s
d) 3.72 s
e) 3.14 s
15) Before CD’s were invented, we used to listen to music on thin pieces of plastic with
groves in them called records. Suppose you put a penny on a record and let it spin clockwise
on the turntable. After turning the turntable off, it is still spinning, but is slowing down.
Which arrow shows the direction of the acceleration of the penny at point P during this time
when the turntable is spinning but slowing down.
P
a
b
c
d
e
16) A rider in an amusement park is riding the “barrel of fun” Which diagram correctly
shows the forces acting on her?
a)
c)
b)
d)
e)