
A non-uniform bar of weight is suspended at rest by two strings of negligible weight as shown in Fig. The angles made by the strings with the vertical are and respectively. The bar is long. Calculate the distance of the centre of gravity of the bar from its left end.



Important Questions on Rotation




As shown in figure, a garden roller is pushed with a force of at an angle of with horizontal. The normal reaction on the roller is (Given )


One end of a horizontal uniform beam of weight and length is hinged on a vertical wall at point and its other end is supported by a light inextensible rope. The other end of the rope is fixed at point , at a height above the hinge at point . A block of weight is attached at the point of the beam, as shown in the figure (not to scale). The rope can sustain a maximum tension of . Which of the following statement(s) is(are) correct?

A long ladder weighing leans on a frictionless wall. Its feet rest on the floor away from the wall as shown in the figure. If and are the reaction forces of the floor and the wall, then ratio of will be :
(Use .)

A mass is supported by a massless string wound around a uniform hollow cylinder of mass and radius . If the string does not slip on the cylinder, then with what acceleration will the mass release? (Assume acceleration due to gravity)

A football of radius is kept on a hole of radius made on a plank kept horizontally. One end of the plank is now lifted so that it gets tilted making an angle from the horizontal as shown in the figure below. The maximum value of so that the football does not start rolling down the plank satisfies (figure is schematic and not drawn to scale)

A uniform rod of length and mass is balanced on a wedge placed at mark. A mass of is suspended from the rod at and another unknown mass is suspended from the rod at mark as shown in the figure. Find the value of such that the rod is in equilibrium.


A bead of mass stays at point on a wire bent in the shape of a parabola and rotating with angular speed (see figure). The value of is (neglect friction)





How is it possible to increase the M.A. of the given lever without increasing its length?

The disc of mass with uniform surface mass density is shown in the figure. The centre of mass of the quarter disc (the shaded area) is at the position where is _______ . (Round off to the Nearest Integer) [ is an area as shown in the figure]

A rod of length can rotate about end What is the work done if the rod is rotated by

Shown in the figure is rigid and uniform one meter long rod held in horizontal position by two strings tied to its ends and attached to the ceiling. The rod is off mass and has another weight of mass hung at a distance of from . The tension in the string at is:

Consider a uniform cubical box of side a on a rough floor that is to be moved by applying minimum possible force at a point above its centre of mass (see figure). If the coefficient of friction is , the maximum possible value of for a box not to topple before moving is ________

