Define torque. Give its units.

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Jasmine Grover

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Torque is a measure of the ability of a force to rotate an object around an axis or a pivot. It is also known as the moment of force. Mathematically, torque (τ) is defined as the cross product of the force (F) and the distance (r) from the axis of rotation to the point of application of the force:

τ = r × F

where × denotes the vector cross product.

Torque

The units of torque depends on the units used for force and distance.

  • In the International System of Units (SI), the unit of force is the newton (N) and the unit of distance is the meter (m). Therefore, the unit of torque is the newton-meter (N⋅m).
  • In other systems of units, such as the British engineering system, the unit of force is the pound (lb) and the unit of distance is the foot (ft), so the unit of torque is the pound-foot (lb-ft).
  • The C.G.S unit of torque is dyne-cm.

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CBSE CLASS XII Related Questions

  • 1.

    (I) The real image of an object placed between $f$ and $2f$ from a convex lens can be seen on a screen placed at the image location. If the screen is removed, is the image still there? Explain.

    (II) Plane and convex mirrors produce virtual images of objects. Can they produce real images under some circumstances? Explain.


      • 2.
        Consider the nuclear reaction \( X \to Y + Z \). Let \( M_x \), \( M_y \), and \( M_z \) be the masses of the three nuclei X, Y, and Z respectively. Then which of the following relations hold true?

          • \( (M_x - M_z)<M_y \)
          • \( (M_x - M_y)<M_z \)
          • \( M_x>(M_y + M_z) \)
          • \( M_x<(M_y + M_z) \)

        • 3.

          A circular coil of 100 turns and radius $\left(\frac{10}{\sqrt{\pi}}\right)$ cm carrying current of $5.0\,\text{A}$ is suspended vertically in a uniform horizontal magnetic field of $2.0\,\text{T}$. The field makes an angle $30^\circ$ with the normal to the coil. Calculate:

          (I) the magnetic dipole moment of the coil, and

          (II) the magnitude of the counter torque that must be applied to prevent the coil from turning.


            • 4.
              Two point charges -Q and Q are located at points (d, 0) and (0, d) respectively, in x-y plane. The electric field E at the origin will be:

                • \(\frac{1}{4\pi\epsilon_0} \frac{\sqrt{2}Q}{d^2} (\hat{i} - \hat{j})\)
                • \(\frac{1}{4\pi\epsilon_0} \frac{\sqrt{2}Q}{d^2} (-\hat{i} - \hat{j})\)
                • \(\frac{1}{4\pi\epsilon_0} \frac{Q}{d^2} (\hat{i} - \hat{j})\)
                • \(\frac{1}{4\pi\epsilon_0} \frac{Q}{d^2} (-\hat{i} - \hat{j})\)

              • 5.

                A parallel beam of monochromatic light falls normally on a single slit of width $a$ and a diffraction pattern is observed on a screen placed at distance $D$ from the slit. Explain:

                (I) the formation of maxima and minima in the diffraction pattern, and

                (II) why the maxima go on becoming weaker and weaker with its increasing number $n$.


                  • 6.

                    A ray of light MN is incident normally on the face corresponding with side AB of a prism with an isosceles right-angled triangular base ABC. Trace the path of the ray as it passes through the prism when the refractive index of the prism material is (i) $\sqrt{2}$, and (ii) $\sqrt{3}$.

                      CBSE CLASS XII Previous Year Papers

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