A spring of force constant 800 N/m has an extension of 5cm. The work done in extending it from 5cm to 15 cm is:

(1) 16 J

(2) 8 J

(3) 32 J

(4) 24 J

A spring of spring constant 5 × 10³ N/m is stretched initially by 5cm from the unstretched position. Then the work required to stretch it further by another 5 cm is 

(1) 6.25 N-m

(2) 12.50 N-m

(3) 18.75 N-m

(4) 25.00 N-m

A mass of 0.5kg moving with a speed of 1.5 m/s on a horizontal smooth surface, collides with a nearly weightless spring of force constant k = 50 N/m. The maximum compression of the spring would be 

(1) 0.15 m

(2) 0.12 m

(3) 1.5 m

(4) 0.5 m

A particle moves in a straight line with retardation proportional to its displacement. Its loss of kinetic energy for any displacement x is proportional to- 

(1) x²

(2) e^x

(3) x

(4) log_e x

The spring extends by x on loading, then energy stored by the spring is : (if T is the tension in spring and k is spring constant) 

(1) $\frac{T^2}{2k}$

(2) $\frac{T^2}{2k^2}$

(3) $\frac{2k}{T^2}$

(4) $\frac{2T^2}{k}$

The potential energy of a body is given by, U = A – Bx² (Where x is the displacement). The magnitude of force acting on the particle is 

(1) Constant

(2) Proportional to x

(3) Proportional to x²

(4) Inversely proportional to x

The potential energy between two atoms in a molecule is given by $U\left ( x \right )=\frac{a}{x^{12}}-\frac{b}{x^{6}};$ where $a$ and $b$ are positive constants and $x$ is the distance between the atoms. The atoms are in stable equilibrium when:
1. $x=\sqrt[6]{\frac{11a}{5b}}$
2. $x=\sqrt[6]{\frac{a}{2b}}$
3. $x=0$
4. $x=\sqrt[6]{\frac{2a}{b}}$

Which one of the following is not a conservative force 

(1) Gravitational force

(2) Electrostatic force between two charges

(3) Magnetic force between two magnetic dipoles

(4) Frictional force

Work done in raising a box depends on

(1) How fast it is raised

(2) The strength of the man

(3) The height by which it is raised

(4) None of the above