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Unformatted text preview: PHYSCS4A EXAMS CHAPTER3942 SUMNERZMOEHFORMP\
NAME K
LD#
QGNATURE GRADE 1. A hockey puck (small hard solid disk) 8 rests on a smooth ice surface and is struck in a
second puck A, which was originally traveling at 40.0 We and which is deﬂected 30.0
from its original direction as in the ﬁgure below. Fuck 8 acquires a veiocity at a 45° angie
to the original direction of A. The pucks have the same mass. Compute the speed of
each puck after the collision. 2. A device for measuring moment of inertia of an object is shown in the figure below. A
circular piatform has a concentric drum of radius 10 cm about which a string is wound. _
The string passes over a frictionless puliey to a weight of mass M. The weight is ‘
released from rest, and the time to drop a distance D is measured. The system is then
rewound, the object placed on the platform, and the system is again reieased from rest.
The time required for the weight to drop the same distance D then provides the data
needed to calculate i (moment I rotational inertiaWVith M = 2.5 kg and D = 1.8 m, the time
is 4.2 s. (a) Find the combined moment of inertia of the platform, drum, shaft. and puiley.
(b) With the object placed on the platform, the time is 6.8 s for D = 1.8 m. Find 1 of that
object about the axis of the platform. " mew
R233
5,.
i A 360kg object is supported on a wire attached to a 15m—long steel bar that is pivoted at
a vertical wait and supported by a cable as shown in the ﬁgure beiow‘ The mass of the
bar is 85.0 kg. With the cable attached to the bar 5.0 m from the tower end as shown,
ﬁnd the tension in the cable and the force exerted by the wall (or hinge) on the steet bar
(magnitude and direction) To clarify the diagram. The angie between the steel bar and
the welt is 600. The angie the cable makes with the steel bar is 90”. A sotid wood door 1.00 m wide and 2.00 m hégh is hinged atong one side and has a totat
mass of 50.0 kg {1 m 1I3Ma2 ; where a is the width of the door). tnitéatty open and at rest,
the door is struck at its center by a handfu! of stécky mud of mass 0.500 kg, traveling
12.0 mls 311st before impact. Find the ﬁnal angutar veiocity of the door. Assume the velocity of the mud is perpendicutar to the piane of the door. 5. Seiect the best answer for the muitiple choice question and write that answer in the
’3 space provided next to the question. AWWtm 55;; 1) The center of mass of the system consisting of Earth, the Sun. and the pianet Mars is:
a) closer to Earth than to either of the other bodies
b) cioser to the Sun than to either of the other bodies
c) closer to Mars than to either of the other bodies
d) at the geometric center of the triangte formed by the three bodies
e) at the center of the tinejoining Earth and Mars i:
g i 2) A particle moves atong the x axis. its momentum is graphed beiow as a function of time.
Rank the numbered regions according to the magnitude of the force acting on the particle,
feast to greatest. VS; 3) Two carts (A and 8). having spring bumpers, collide as shown. Cart A has a mass of 2 kg
and is lnitiaiiy moving to the right. Cart 8 has a mass of 3 kg and is initiatiy stationary. When
the separation between the carts is a minimum (Maximum compression of springs): a) cart B is stiti at rest
h) cart A has come to rest
0) the carts have the same momentum
a, d) the carts have the same kinetic energy
' e) the kinetic energy of the system is at a minimum W" 4) if a whee! turns with constant anguiar speed then:
a) each point on its rim moves with constant velocity
is) each point on its rim moves with constant acceleration
c) the wheel turns through equal angies in equai times
:3) the angle through which the wheel turns in each second increases as time goes on
e) the angle through which the wheei turns in each second decreases as time goes on > T? f if
is r; g?
wt em To increase the rotational inertia of a solid disk about its axis without changing its mass: a) drill holes near the rim and put the material near the axis b) drill holes near the axis and put the material near the rim c) drill holes at points on a circle near the rim and put the material at points between the
holes (1) drill holes at points on a circle near the axis and out the material at points between the
holes a) do none of the above (the rotational inertia cannot be changed without changing the
mass) A wheel rolls without sliding along a horizontal road as shown. The velocity of the center of the wheel is represented by > . Point P is painted on the rim of the wheel. The
instantaneous velocity of point P is: a) “i
b} e
c) ‘i
d) 2
e} zero A man. with his arms at his sides, is spinning on a light frictionless turntable. When he
extends his arms: a) his angular velocity increases b) his angular velocity remains the same 6) his rotation inertia decreases d) his rotational kinetic energy increases a) his angular momentum remains the same Two pendulum bobs of unequal mass are suspended from the same ﬁxed point by strings of
equal length. The lighter hob is drawn aside and then released so that it collides with the
other bob on reaching the vertical position. The collision is completely elastic. What
quantiﬁes are conserved in the collision? a) both kinetic energy and angular momentum of the system b) only kinetic energy c) only angular momentum d) angular speed of light bob e) none of the above For a body to be in equilibrium under the combined action of several forces:
a) all the forces must he applied at the same point b) all of the forces form pairs of equal and opposite forces 0) any two of these forces must be balanced by a third force d) the sum of the torques about any point must equal zero e) the lines of action of all the forces must pass through the center of gravity of the body é; a
E S we 10) A horizontaé beam of weight W is supported by a hinge and cable as shown. The force
exerted on the beam by the hinge has a vertical component that must be: cabie hinge @ a) nonzero and up b) nonzero and down 0) nonzero but not enough information is given to know whether up or down
6) zero 8) equai to W ...
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 Spring '10
 Carter
 mechanics

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