Elasticity

Q.

For a given material, the Young's modulus is 2.4 times that of rigidity modulus. Its Poisson's ratio is

1. 2.4

2. 1.2

3. 0.4

4. 0.2

Q. Two wires A and B are made of same material. The wire A has a length l and diameter r while the wire B has length 2l and diameter 2r. If the two wires are stretched by the same force, the elongation in A divided by elongation in B is

1. 

2. 

3. 

4. 

Q.

Give one word for the property by which the matter regains back its original state.

Q. 29.The ABC is a triangular plate of uniform thickness. The sides are in the ratio shown in the figure. I AB, IBC and I CA are the moments of inertia of the plate about AB, BC and CA respectively. Which one of the following relations is correct?

Q. If the gas expands against vaccum then the work done is zero .How

Q. A material which stretches more is more elastic.

1. False
2. True

Q. A bull of mass m is moving towards a player withvelicity v. If player stopped it, then impulseapplied by the player is(2) +mv-mv(4) +2mv(3) -2mvxoot? why it is not +mv

Q. five masses are placed on the vertices of a recular pentagon a sixth mass is placed at the center of pentagon then resul†an t force on mo

Q. 55.An equilateral triangle has mass "m" on all its vertices, what is the force acting on the centroid of mass "2m"?

Q. The proportional limit of steel is 8×10 N/m and Y=2×10 N/m. The maximum elongation , a one meter long steel wire can be given without exceeding the elastic limit is

Q. In an elastic solid, the work done by an external force to produce strain is $800\text{J}$. If the external force is removed, then the elastic potential energy of the solid will be -

1. $800\text{J}$
2. $400\text{J}$
3. $200\text{J}$
4. $0\text{J}$

Q. The relationship between Young's modulus Y, Bulk modulus K and modulus of rigidity $\eta$ is

1. $y=\frac{9\eta k}{\eta +3K}$
2. $y=\frac{9YK}{Y+3K}$
3. $y=\frac{9\eta k}{3+K}$
4. $y=\frac{3\eta k}{9\eta +K}$

Q. If in a wire of Young's modulus $Y$, longitudinal strain $X$ is produced, then the elastic potential energy stored in its unit volume will be

1. $2Y{X}^2$
2. $0.5Y{X}^2$
3. $0.5Y^{2}X$
4. $Y{X}^2$

Q. The property of a material to restore its natural shape or to oppose deformation is called

1. Rigidity
2. Elasticity
3. Plasticity
4. Deformability

Q. If an elastic film can be modelled as a square grid formed by a very small spring each of stiffness k.show that potential energy U OF THE FILM if stretched uinformally and isotropically in all directions is given by U=K(√S-√So)^2.here So is the area of unstreched film and S is area of stretched film.Now such an elastic film is used to fabricate a spherical ballon of radius ro in relaxed state.Find the dependence of air pressure p inside the ballon on its radius r.Assume vacuum outside the ballon.

Q. Two wires, one of steel and another of aluminium, each of 2m length and diameter of 2mm are joined end to end to form a composite wire of length 4m. What tension in the wire will produce a total extension of 0.9mm

Q. Three bars of copper ( modulus of elasticity Y)having length L and 2L and 3 l and area of cross section A, 2A and 3A are joined rigidly end-to-end compound rod subjected to a stretching force f find the net modulus of elasticity of the system of wires.

Q. A steel wire of length $5\text{m}$ is suspended vertically, stretches by $20\text{mm}$ when mass of $60\text{kg}$ is attached to the lower end. Find the elastic potential energy gained by the wire. (take $g=10{\text{m/s}}^2$)

1. $0.6\text{J}$
2. $6\text{J}$
3. $60\text{J}$
4. $600\text{J}$

Q. a)AR21. The normal density of gold is ρ and its modulus1B. The increase in density of piece of gold ihespressure P is applied uniformly from all sides) 283) B-P2P(4) B-P22. A wire of length 5 m is twisted through 30\ast at freend. If the radius of wire is 1 mm, the shearingstrain in the wire is

Q. The diagram shows a force-extension graph for a rubber band. Consider the following statements




I.It will be easier to compress this rubber than expand it
II.Rubber does not return to its original length after it is stretched
III.The rubber band will get heated if it is stretched and released
Which of these three statements can be deduced from the graph?

1. III only
2. II and III
3. I and III
4. I only

Q. A steel wire of length $5\text{m}$ is suspended vertically, stretches by $20\text{mm}$ when mass of $60\text{kg}$ is attached to the lower end. Find the elastic potential energy gained by the wire. (take $g=10{\text{m/s}}^2$)

1. $0.6\text{J}$
2. $6\text{J}$
3. $60\text{J}$
4. $600\text{J}$

Q. When a uniform metallic wire is stretched the lateral strain produced in it is $\beta$. If $\nu$ and $Y$ are the Poisson's ratio and Young's modulus for the wire, then elastic potential energy density of wire is

1. $\frac{Y{\beta }^2}{2}$
2. $\frac{Y{\beta }^2}{2{\nu }^2}$
3. $\frac{Y\nu {\beta }^2}{2}$
4. $\frac{Y{\nu }^2}{2\beta }$

Q.

A body is said to be perfectly elastic if

1. it is not effected by external force

2. its surface is perfectly smooth

3. it can move freely

4. it recovers its original shape / size when the deforming force is removed

Q. Elasticity has a different meaning in physics than that of daily life. Comment.

Q.

The wires A and B shown in the figure are made of the same material, and have radii r_A and r_B respectively. The block between them has a mass m. When the force F is mg/3, one of the wires breaks.

1. A will break before B if $r_A=r_B$
2. A will break before B if $r_A=r_B$
3. Either A or B may break if $r_A<2r_B$

4. The lengths of A and B must be known to predict which wire will break

Q. If the volume of the given mass of a gas is increased four times, the temperature is raised from ${27}^{\circ }$;C to ${127}^{\circ }$;C. The elasticity will become

1. 4 times
2. $\frac{1}{4}$ times
3. 3 times
4. $\frac{1}{3}$ times

Q. If in a wire of Young's modulus $Y$, longitudinal strain $X$ is produced, then the elastic potential energy stored in its unit volume will be

1. $0.5Y{X}^2$
2. $0.5Y^{2}X$
3. $2Y{X}^2$
4. $Y{X}^2$

Q. A wire can sustain a weight of $20\text{kg}$ before breaking. If the wire is cut into two equal parts, each part can sustain a weight of

1. $10\text{kg}$
2. $20\text{kg}$
3. $05\text{kg}$
4. $25\text{kg}$
   

Q. kE of a body is incresed by 44% .what is the percent increase in momentu

Q.

What will be the nature of inter-atomic forces when deforming force applied on anobject (i) increases, (ii) decreases the inter-atomic separation?