# 大學普通物理

3. A 2.0-kg block travels around a 0.50 m radius circle with an angular

speed of 12 rad/s. The circle is parallel to the xy plane and is

centered on the z axis, 0.75 m from the origin. The magnitude of the

angular momentum around the origin is:

A) 6.0 kg &middot;m2/s D) 14 kg &middot;m2/s

B) 9.0 kg &middot;m2/s E) 20 kg &middot;m2/s

C) 11 kg &middot;m2/s

4. If a body is spinning about a principal axis then:

A) the torque acting on it must be perpendicular to the axis

B) the torque acting on it must be along the axis

C) its angular momentum must be along the axis

D) its angular momentum must he perpendicular to the axis

E) none of the above

8. A man, holding a weight in each hand, stands at the center of a

horizontal frictionless rotating turntable. The effect of the

weights is to double the rotational inertia of the system. As he is

rotating, the man opens his hands and drops the two weights. They

fall outside the turntable. Then:

A) his angular velocity doubles

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B) his angular velocity remains about the same

C) his angular velocity is halved

D) the direction of his angular momentum vector changes

E) his rotational kinetic energy increases

11. A cube with 2.0-cm sides is made of material with a bulk modulus of

4.7x105 N/m2. When it is subjected to a pressure of 2.0x105 Pa the

length in cm of its any of its sides is:

A) 0.85 D) 2.0

B) 1.15 E) none of these

C) 1.66

12. A uniform U-tube is partially filled with water. Oil, of density

0.75 g/cm3, is poured into the right arm until the water level in

the left arm rises 3 cm. The length of the oil column is then:

A) 2.25 cm

B) 8 cm

C) 6 cm

D) 4 cm

E) need to know the cross-sectional area of the U-tube

17. Consider a pipe containing a fluid, with the fluid being at rest. To

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apply Bernoulli&#039;s equation to this situation:

A) set v equal to zero because there is no motion

B) set g equal to zero because there is no acceleration

C) set v and g both equal to zero

D) set p equal to the atmospheric pressure

E) cannot be done, Bernoulli&#039;s equation applies only to fluids in

motion

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