Physics
Rotational and Circular Motion
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#121 A mass $m=2\,\text{kg}$ moves in a circle of radius $r=2\,\text{m}$ with speed $v=4\,\text{m s}^{-1}$. The required centripetal force is:
A) $mvr$
B) $\dfrac{v}{mr}$
C) $\dfrac{r}{mv^{2}}$
D) $\dfrac{mv^2}{r}$
#122 Choose the correct set of analogies:
A) $F\leftrightarrow \omega,\ a\leftrightarrow I,\ m\leftrightarrow\tau$
B) $F\leftrightarrow I,\ a\leftrightarrow\tau,\ m\leftrightarrow\alpha$
C) $F\leftrightarrow a,\ m\leftrightarrow\tau,\ I\leftrightarrow\alpha$
D) $F\leftrightarrow \tau,\ a\leftrightarrow\alpha,\ m\leftrightarrow I$
#123 A mass $m=1\,\text{kg}$ moves in a circle of radius $r=5\,\text{m}$ with speed $v=4\,\text{m s}^{-1}$. The required centripetal force is:
A) $mvr$
B) $\dfrac{v}{mr}$
C) $\dfrac{mv^2}{r}$
D) $\dfrac{r}{mv^{2}}$
#124 In absence of external torque, a spinning body tends to:
A) reverse spin spontaneously
B) keep its angular momentum vector constant
C) lose all rotational KE
D) double its angular speed
#125 Work done by a constant torque $\tau$ through angle $\theta$ is:
A) $W=\tau\,\theta$
B) $W=\alpha\theta$
C) $W=\tau/\theta$
D) $W=I\omega$
#126 On a frictionless banked curve of radius $r$ and bank angle $\phi$, the ideal speed is:
A) $v=\sqrt{g/\tan\phi}$
B) $v=\sqrt{rg\tan\phi}$
C) $v=rg\phi$
D) $v=\sqrt{gr\tan\phi}$
#127 A mass $m=4\,\text{kg}$ moves in a circle of radius $r=2\,\text{m}$ with speed $v=10\,\text{m s}^{-1}$. The required centripetal force is:
A) $\dfrac{r}{mv^{2}}$
B) $\dfrac{mv^2}{r}$
C) $mvr$
D) $\dfrac{v}{mr}$
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