The breaking stress of a wire depends upon

• length of  the wire

• material of the wire

• radius of the wire

• shape of the cross-section

Assertion: Stress is the internal force per unit area of a body.

Result: Rubber is more elastic than steel.

• If both the assertion and reason are true and reason is a correct explanation of the assertion.

• If both assertion and reason are true but assertion is not a correct explanation of the assertion.

• If the assertion is true but the reason is false.

• If both assertion and reason are false.

A body weighs 200 N at the surface of earth. If it be placed in an artificial satellite revolving at height where acceleration due to gravity is half of that at earth's surface. It will weigh

• 2$\times$10⁹ N/m²

• 2 $\times$10⁸ N/m²

• 2$\times$10⁶ N/m²

• 2$\times$ 10⁴ N/m²

A metal wire of length l, area of cross-section A and Young's modulus Y behaves as a spring of spring constant k given by

• $\mathrm{k}= \frac{\mathrm{YA}}{\mathrm{l}}$

• $\mathrm{k}= \frac{2\mathrm{YA}}{\mathrm{l}}$

• $\mathrm{k}= \frac{\mathrm{YA}}{2\mathrm{l}}$

• $\mathrm{k}= \frac{\mathrm{Yl}}{\mathrm{A}}$

The breaking strength of a rod of diameter 2 cm is 2x 10⁵ N. Then that for rod of same material but diameter 4 cm will be

• 2 × 10⁵ N

• 1 × 10⁵ N

• 8 × 10⁵ N

• 0.5 × 10⁵ N

A metallic rod of Young's modulus 2x10¹¹ N/m² undergoes a strain of 0.5%. Then the energy stored per unit volume in the rod will be

• 2.5 × 10⁶ J/m³

• 5 × 10⁸ J/m³

• 2.5 × 10⁸ J/m³

• 0.5 × 10¹¹ J/m³

A bob of mass 10 kg is attached to wire 0.3 m long. Its breaking stress is 4.8 x10⁷ N/m2. The area of cross-section of the wire is 10^-6 m². The maximum angular velocity with which it can be rotated in a horizontal circle is

• 8 rad/s

• 4 rad/s

• 2 rad/s

• 1 rad/s

A rubber cord 10 m long is suspended vertically. How much does it stretch under its own weight? (Density of rubber is 1500 kg/m³, Y = 5 × 10⁸ N/m², g = 10 m/s²)

• 15 × 10^-4 m

• 7.5 × 10^-4 m

• 12 × 10^-4 m

• 25 × 10^-4 m

A brass rod of cross-sectional area 1 cm² and length 0.2 m is compressed lengthwise by a weight of 5 kg of Young's modulus of elasticity of brass is 1 x 10¹¹ N/m² and g = 10 m/s², then increase in the energy of the rod will be

• 10^-5 J

• 2.5 × 10^-5 J

• 5 × 10^-5 J

• 2.5 × 10^-4 J

50.

A wire fixed at the upper end stretches by length $\mathrm{\Delta l}$ by applying a force F. The work done in stretching is

• $\frac{\mathrm{F}}{2\mathrm{\Delta l}}$

• FΔl

• 2 FΔl

• $\frac{\mathrm{F\Delta l}}{2}$