Exams › JEE Main › Physics

A cuboidal block with edges a, b and c rests on the ground (its base being the face of dimensions a by b). A horizontal force F applied to the top face produces a small shear, tilting it by angle phi. If eta is the modulus of rigidity, what is phi?

1. F/(a*b*eta)
2. F/(a*c*eta)
3. F/(b*c*eta)
4. F/(sqrt(b² + c²)*eta)

Correct answer: F/(a*b*eta)

Solution

The shearing force F acts over the top area a*b, so shear stress = F/(ab); with eta = stress/phi, the deformation angle phi = F/(ab*eta).

Related JEE Main Physics questions

• Select the incorrect statement.
• A steel wire has length l and cross-sectional area A. When a certain load is applied, it elongates by 1 cm. If the same load is now applied to another steel wire made of the same material, having twice the length and half the cross-sectional area, what will be its extension?
• For common metals such as aluminium and copper, which sequence correctly represents the relative magnitudes of the elastic moduli?
• A steel sheet fails under a shear stress of 3.5 × 10⁸ N m⁻². The approximate force required to punch a circular hole of diameter 1 cm through a steel plate 0.3 cm thick is:
• A copper wire of fixed volume V is stretched out to a length l. If a constant force F is applied to this wire and it elongates by Δl, which of the following plots would be a straight line?
• A material has Poisson’s ratio equal to 0.5. When a tensile force is applied to a wire made of this material, its cross-sectional area decreases by 4%. The corresponding percentage increase in its length is:

⚔️ Practice JEE Main Physics free + battle 1v1 →