Physics
Rotational and Circular Motion
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#81 In absence of external torque, a spinning body tends to:
A) lose all rotational KE
B) keep its angular momentum vector constant
C) double its angular speed
D) reverse spin spontaneously
#82 Moment of inertia of a solid disc about the standard axis is:
A) $I=ML^{2}$
B) $I=\tfrac34 MR^{2}$
C) $I=\tfrac12 MR^{2}$
D) $I=\tfrac23 MR^{2}$
#83 Moment of inertia of a solid disc about the standard axis is:
A) $I=\tfrac34 MR^{2}$
B) $I=\tfrac12 MR^{2}$
C) $I=\tfrac23 MR^{2}$
D) $I=ML^{2}$
#84 Moment of inertia of a thin rod (center) about the standard axis is:
A) $I=ML^{2}$
B) $I=\tfrac{1}{12}ML^{2}$
C) $I=\tfrac23 MR^{2}$
D) $I=\tfrac34 MR^{2}$
#85 Choose the correct set of analogies:
A) $F\leftrightarrow I,\ a\leftrightarrow\tau,\ m\leftrightarrow\alpha$
B) $F\leftrightarrow a,\ m\leftrightarrow\tau,\ I\leftrightarrow\alpha$
C) $F\leftrightarrow \omega,\ a\leftrightarrow I,\ m\leftrightarrow\tau$
D) $F\leftrightarrow \tau,\ a\leftrightarrow\alpha,\ m\leftrightarrow I$
#86 A mass $m=2\,\text{kg}$ moves in a circle of radius $r=5\,\text{m}$ with speed $v=4\,\text{m s}^{-1}$. The required centripetal force is:
A) $\dfrac{mv^2}{r}$
B) $\dfrac{v}{mr}$
C) $mvr$
D) $\dfrac{r}{mv^{2}}$
#87 For a rigid body rolling without slipping, total kinetic energy equals:
A) $I\omega$
B) $\tfrac12 mv^{2}+\tfrac12 I\omega^{2}$
C) $\tfrac12 mv^{2}$
D) $\tfrac12 I\omega^{2}$
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