Show that work done by a stretching force in producing an extension in the wire is given by `W=frac(1)(2)xx stretching force xx extension`.

The work done per unit volume in stretching a wire is equal to

Show that energy density =frac(1)(2) xx stress xx strain.

Show that the work done by an external force in bringing a unit positive charge from infinity to a point is equal to electrostatic potential (V) at that point.

The rotational K.E. is given by frac(1)(2) I omega^2 . Use this equation to obtain dimension of I.

A wire of length L and radius r is fixed at one end and a force F applied to the other end produces an extension l. the extension produced in another wire of same material of length 2L and radius 2r by a force 2F is

K is the force constatnt of a spring . The work done in extending it from l1to l2 is

A rain drop of radius 2 mm falls from a height of 500 m above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is 10 m s-^1 ?

In stretching a wire , workmhas to be done . What happens to this work ?

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

In a primary school parents asked about of the number of hours they spend per day in helping their children to do home work. There were 90 parents who helped for frac(1)(2) hour to 1frac(1)(2) hours. The distribution of parents according to the time for which, they said they helped is given in the adjoining figure, 20% helped for the than 1frac(1)(2) hours per day, 30% helped for frac(1)(2) hour to 1 hours, 50% did not help at all. Using this, answer the following : How many said that they helped more than 1frac(1)(2) hours?