Download Rotational Motion Practice MC Answers

AP Physics 1Rotational
1.
Which factor does the torque on an object
Practice Multiple
d_epend on?
Choice
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magnitude of the applied force
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object's angular velocity
angle at which the force is applied
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distance from the axis to the point at which the force is applied
A.
The
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C. The
D. The
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2.
not
Motion
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A door (seen from above in the figures below) has hinges on the left hand side. Which force produces the
3rgest torque? The magnitudes of all forces are equal.
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3.
In which of the following diagrams is the torque about point 0 equal in magnitude to the torque about point
X in the diagram? (All forces lie in the plane of the paper.)
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5.
Pairs of forces
a.
6.
7.
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A system of two wheels fixed to each other is free to rotate about a frictionless axis
through the common center of the wheels and perpendicular to the page. Four
forces are exerted tangentially to the rims of the wheels, as shown. The magnitude
of the n t torgue on the system about the axis is
(A) zero
~FR
(C) 5FR
(D) 14FR
act on identical
n
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4.
of equal magnitude
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cylinders
as shown
in the figures.
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c.
d.
e. /
A uniform meterstick of mass' 0.20 kg is pivoted at the 40 cm mark. At what mark on the meterstick should
one ang a mass'of 0.50 kg to balance the stick?
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(A) 16 cm
fl1 36 cm
(C) 44 cm
(D) 46 em
c.~
A uniform meterstick is balanced at its midpoint with
several forces applied as shown below. If the stick is in
equilibrium, the magnitude of the force X in newtons (N) is
50 N (8) 100 N (C) 200 N (D) 300 N
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To weigh a fish. a person hangs a tackle box of mass 3.5 kilograms and a cooler of mass 5 kilograms from
the ends of a uniform rigid pole that is suspended by a rope attached to its center. The system balances
when the fish hangs at a point 1/4 of the rod's length from the tackle box. What is the mass of the fish?
(A) 1.5 kg (6) 2 kg
~)"'3 kg");?
(D) 6 kg
Disk 2
Disk 1
9.
Choice
Two uniform disks have the same mass but different
radii: disk 1has a Radius R, disk 2 has a radius 2R.
What is the ratio between the moment of inertia of the second disk to the first disk?
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B. .':
c. 3.
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10. Rasheed and Sofia are riding a merry-go.round that is spinning steadily. Sofia is twice
as far from the axis as is Rasheed. Sofia's angular veiocitl' is
that of Rasheed.
A. Half
@Thesameas
C. Twice
D.
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Four times
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11. Rasheed and Sofia are riding a merry-go-round
that is spinning steadily as seen
above. Sofia is twice as far from the axis as is Rasheed. Sofia's speed is.
A. Half
that of Rasheed.
B.
The same as
Twice
D. Four times
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turns through an angle of 2S rad in a time t.
12. Starting from rest, a wheel with constant angular acceleration
Through what angle will it have turned after time3fl..
A.
B.
25 rad
50 rad
c.
@
75 rad
100 rad
E.
200 rad
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13. The fan blade is speeding up. What are the signs of
A. OJ is positive and a is positive.
B.
C.
~
OJ
is positive and a is negative.
is negative and a is positive.
OJ
is negative and
OJ
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a is negative.
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AP Physics 1 Rotational Motion Practice Multiple Choice
14. Earth moves around the Sun in an elliptical orbit. The Earth approaches the closets point to the Sun its
linear velocity increases. Which of the following doesn't changes during the Earth's motion?
A. The
B. The
C. The
The
(9)
orbital radius
kinetic energy
potential energy
angular momentum
15. An ice skater performs a fast spin by pulling outstretched
arms down and close to her body. What happens
to her angular mOillentl,lm with respect to the axis of rotation?
A. It increases
B. It decreases
C t doesn't change
D. It depends how fast she rotates
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16. An ice skater performs a fast spin by pulling outstretched
arms down and close to her body. What happens
to her kinetic energy_with respect to the axis of rotation?
~It
increases
B. It decreases
C. It doesn't change
D. It depends how fast she rotates
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17.
An asteroid traveling through space collides with one end of a long, cylindrical satellite as
shown above, and sticks to dle satellite. \'\'lllch of the following is erue of dle isolated
asteroid-satellite system in tllls collision?
a. Kinetic energy K is conserved
b. Total Energy E is conserved, but angular momenmm L is not conserved
c. Angular momentum L is conserved, but linear momenrtun p is not conservcd
J Angular momenrtlm L is conserved, and total energy E is conserved
e. Linear momentum p is conselved but angular momentum L is not conserved
AP Physics 1 Rotational
Motion Practice Multiple
Choice
Answers:
1. B Torque = F r sinS
2. C All forces are equal so the perpendicular
force applies more torque
3. C If one calculates the torques for each a) 0, b) Fr/2 c) 2Frsin 30 (the angle given is the opposite of the angle
that gives the perpendicular component of the force) d) 2FRsin60 again the angle is the opposite of the
one needed.
4. B (3FR + 3FR + 2FR - 6FR)
5. B all other forces would cause either rotation or translation
or both
6. B O.SgX = .2g(1O) x = 4cm from pivot or 36 cm on meterstick
7. A 20X + 200(40) = 300(30)
8. C 3.Sg(L/2) + Xg(L/4) = Sg(L/2)
9. D I is proportional
to r' so Disk 2 has 4x the I of disk 1
10. B angular velocity is not dependent on radius
11. C velocity is dependent
on r, so 2x r means 2x speed.
12. D when an object accelerations
S is proportional
doubles then distance goes up by 4
13. D clockwise is the - direction so
Cll-.
to t' (displacement
kinematic equation) so if time
An object speeding up in the - direction is - acceleration.
14. D An objects angular momentum is conserved in the absence of an external force. The force of gravity
between the planets is an internal force so the linear velocity increases because the radius decreases due
to the conservation of angular momentum.
15. C angular momentum
is conserved in the absence of an external force
16. A because angular momentum
the same amount.
is conserved the skaters I decreases but her angular velocity increases by
Since rotation kinetic energy =
ICll',
the change increases her kinetic energy.
17. D Because there are no external forces or torques (outside the asteroid and satellite),
both linear
momentum is and angular momentum and total energy is conserved. Kinetic energy is oniy conserved in a
elastic collision and since the asteroid sticks to the satellite then is an total INELASTIC collision.