02. Torque, Angular Momentum
Rotational Motion

149942 A disc of moment of inertia ' \(I_{1}\) ' is rotating with angular velocity ' \(\omega_{1}\) ' about an axis perpendicular to its plane, passing through its centre. If another disc of moment of inertia ' \(I_{2}\) ' about the same axis is gently placed over it, then the new angular velocity of the combined disc will be

1 \(\frac{\left(\mathrm{I}_{1}+\mathrm{I}_{2}\right) \omega_{1}}{\mathrm{I}_{1}}\)
2 \(\frac{I_{2} \omega_{1}}{I_{1}+I_{2}}\)
3 \(\frac{I_{1} \omega_{1}}{I_{1}+I_{2}}\)
4 \(\omega_{1}\)
Rotational Motion

149943 Force \(\overrightarrow{\mathbf{F}}\) is acting on a particle having position vector \(\overrightarrow{\boldsymbol{r}}\). Let \(\vec{\tau}\) be the torque of this force about the origin. The correct equation is

1 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau}=0\)
2 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau}=0\)
3 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau} \neq 0\)
4 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau} \neq 0\)
Rotational Motion

149944 A torque of \(50 \mathrm{Nm}\) acts on a body for 8 second which is initially at rest. The change in its angular momentum is

1 \(400 \mathrm{kgm}^{2} / \mathrm{s}\)
2 \(800 \mathrm{kgm}^{2} / \mathrm{s}\)
3 \(1000 \mathrm{kgm}^{2} / \mathrm{s}\)
4 \(600 \mathrm{kgm}^{2} / \mathrm{s}\)
Rotational Motion

149945 A \(20 \mathrm{~kg}\) flywheel in the form of a uniform circular disc, \(1 \mathrm{~m}\) in diameter is making 120 rpm. What is its angular momentum?

1 \(3.14 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}\)
2 \(31.4 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
3 \(314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
4 \(0.314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
Rotational Motion

149942 A disc of moment of inertia ' \(I_{1}\) ' is rotating with angular velocity ' \(\omega_{1}\) ' about an axis perpendicular to its plane, passing through its centre. If another disc of moment of inertia ' \(I_{2}\) ' about the same axis is gently placed over it, then the new angular velocity of the combined disc will be

1 \(\frac{\left(\mathrm{I}_{1}+\mathrm{I}_{2}\right) \omega_{1}}{\mathrm{I}_{1}}\)
2 \(\frac{I_{2} \omega_{1}}{I_{1}+I_{2}}\)
3 \(\frac{I_{1} \omega_{1}}{I_{1}+I_{2}}\)
4 \(\omega_{1}\)
Rotational Motion

149943 Force \(\overrightarrow{\mathbf{F}}\) is acting on a particle having position vector \(\overrightarrow{\boldsymbol{r}}\). Let \(\vec{\tau}\) be the torque of this force about the origin. The correct equation is

1 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau}=0\)
2 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau}=0\)
3 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau} \neq 0\)
4 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau} \neq 0\)
Rotational Motion

149944 A torque of \(50 \mathrm{Nm}\) acts on a body for 8 second which is initially at rest. The change in its angular momentum is

1 \(400 \mathrm{kgm}^{2} / \mathrm{s}\)
2 \(800 \mathrm{kgm}^{2} / \mathrm{s}\)
3 \(1000 \mathrm{kgm}^{2} / \mathrm{s}\)
4 \(600 \mathrm{kgm}^{2} / \mathrm{s}\)
Rotational Motion

149945 A \(20 \mathrm{~kg}\) flywheel in the form of a uniform circular disc, \(1 \mathrm{~m}\) in diameter is making 120 rpm. What is its angular momentum?

1 \(3.14 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}\)
2 \(31.4 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
3 \(314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
4 \(0.314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
Rotational Motion

149942 A disc of moment of inertia ' \(I_{1}\) ' is rotating with angular velocity ' \(\omega_{1}\) ' about an axis perpendicular to its plane, passing through its centre. If another disc of moment of inertia ' \(I_{2}\) ' about the same axis is gently placed over it, then the new angular velocity of the combined disc will be

1 \(\frac{\left(\mathrm{I}_{1}+\mathrm{I}_{2}\right) \omega_{1}}{\mathrm{I}_{1}}\)
2 \(\frac{I_{2} \omega_{1}}{I_{1}+I_{2}}\)
3 \(\frac{I_{1} \omega_{1}}{I_{1}+I_{2}}\)
4 \(\omega_{1}\)
Rotational Motion

149943 Force \(\overrightarrow{\mathbf{F}}\) is acting on a particle having position vector \(\overrightarrow{\boldsymbol{r}}\). Let \(\vec{\tau}\) be the torque of this force about the origin. The correct equation is

1 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau}=0\)
2 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau}=0\)
3 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau} \neq 0\)
4 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau} \neq 0\)
Rotational Motion

149944 A torque of \(50 \mathrm{Nm}\) acts on a body for 8 second which is initially at rest. The change in its angular momentum is

1 \(400 \mathrm{kgm}^{2} / \mathrm{s}\)
2 \(800 \mathrm{kgm}^{2} / \mathrm{s}\)
3 \(1000 \mathrm{kgm}^{2} / \mathrm{s}\)
4 \(600 \mathrm{kgm}^{2} / \mathrm{s}\)
Rotational Motion

149945 A \(20 \mathrm{~kg}\) flywheel in the form of a uniform circular disc, \(1 \mathrm{~m}\) in diameter is making 120 rpm. What is its angular momentum?

1 \(3.14 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}\)
2 \(31.4 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
3 \(314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
4 \(0.314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
Rotational Motion

149942 A disc of moment of inertia ' \(I_{1}\) ' is rotating with angular velocity ' \(\omega_{1}\) ' about an axis perpendicular to its plane, passing through its centre. If another disc of moment of inertia ' \(I_{2}\) ' about the same axis is gently placed over it, then the new angular velocity of the combined disc will be

1 \(\frac{\left(\mathrm{I}_{1}+\mathrm{I}_{2}\right) \omega_{1}}{\mathrm{I}_{1}}\)
2 \(\frac{I_{2} \omega_{1}}{I_{1}+I_{2}}\)
3 \(\frac{I_{1} \omega_{1}}{I_{1}+I_{2}}\)
4 \(\omega_{1}\)
Rotational Motion

149943 Force \(\overrightarrow{\mathbf{F}}\) is acting on a particle having position vector \(\overrightarrow{\boldsymbol{r}}\). Let \(\vec{\tau}\) be the torque of this force about the origin. The correct equation is

1 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau}=0\)
2 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau}=0\)
3 \(\overrightarrow{\mathrm{r}} . \vec{\tau} \neq 0\) and \(\overrightarrow{\mathrm{F}} . \vec{\tau} \neq 0\)
4 \(\overrightarrow{\mathrm{r}} \cdot \vec{\tau}=0\) and \(\overrightarrow{\mathrm{F}} \cdot \vec{\tau} \neq 0\)
Rotational Motion

149944 A torque of \(50 \mathrm{Nm}\) acts on a body for 8 second which is initially at rest. The change in its angular momentum is

1 \(400 \mathrm{kgm}^{2} / \mathrm{s}\)
2 \(800 \mathrm{kgm}^{2} / \mathrm{s}\)
3 \(1000 \mathrm{kgm}^{2} / \mathrm{s}\)
4 \(600 \mathrm{kgm}^{2} / \mathrm{s}\)
Rotational Motion

149945 A \(20 \mathrm{~kg}\) flywheel in the form of a uniform circular disc, \(1 \mathrm{~m}\) in diameter is making 120 rpm. What is its angular momentum?

1 \(3.14 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}\)
2 \(31.4 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
3 \(314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)
4 \(0.314 \mathrm{~kg} \mathrm{~m}^{2} \mathrm{~S}^{-1}\)