EASY
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A weightless rod is acted upon by upward parallel forces of 2 N and 4 N at ends A and B respectively.
The total length of the rod AB=3 m. To keep the rod in equilibrium a force of 6 N should act in the following manner:
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Important Questions on Rotational Mechanics

MEDIUM

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

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HARD
A uniform wooden stick of mass 1.6 kg and length l rests in an inclined manner on a smooth, vertical wall of height h <l such that a small portion of the stick extends beyond the wall. The reaction force of the wall on the stick is perpendicular to the stick. The stick makes an angle of 30o with the wall and the bottom of the stick is on a rough floor. The reaction of the wall on the stick is equal in magnitude to the reaction of the floor on the stick. The ratio hl and the frictional force f at the bottom of the stick are: g=10 m s-2
MEDIUM
A square loop of side 2a and carrying current I is kept in xz plane with its centre at origin. A long wire carrying the same current I is placed parallel to z-axis and passing through point 0, b, 0, b>>a. The magnitude of torque on the loop about z-axis will be :
MEDIUM

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

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MEDIUM

A 34 m long ladder weighing 10 kg leans on a frictionless wall. Its feet rest on the floor 3 m away from the wall as shown in the figure. If Ff and Fw are the reaction forces of the floor and the wall, then ratio of FwFf will be :
(Use g=10 m s-2.)

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EASY

A rod of length L can rotate about end 0 . What is the work done if the rod is rotated by 180°

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MEDIUM
  Define couple. State the SI unit of moment of couple. 
EASY

As shown in figure, a 70 kg garden roller is pushed with a force of F=200 N at an angle of 30° with horizontal. The normal reaction on the roller is (Given g=10 m s-2)

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MEDIUM
A uniform rod AB is suspended from a point X, at a variable distance x from A, as shown. To make the rod horizontal, a mass m is suspended from its end A. A set of (m, x) value is recorded. The appropriate variables that give a straight line, when plotted, are:

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HARD
An L -shaped object, made of thin rods of uniform mass density, is suspended with a string as shown in figure. If AB=BC, and the angle made by AB with downward vertical is θ, then:
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EASY
Mechanical advantage (MA),  Load (L) and effort (E) are related as :
MEDIUM

Shown in the figure is rigid and uniform one meter long rod AB held in horizontal position by two strings tied to its ends and attached to the ceiling. The rod is off mass 'm' and has another weight of mass 2 m hung at a distance of 75 cm from A. The tension in the string at A is:

 

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MEDIUM
A metre scale is balanced on a knife edge at its centre. When two coins, each of mass 10 g are put one on the top of the other at the 10.0 cm mark the scale is found to be balanced at 40.0 cm mark. The mass of the metre scale is found to be x×10-2 kg. The value of x is _____ .
EASY

The disc of mass M with uniform surface mass density σ is shown in the figure. The centre of mass of the quarter disc (the shaded area) is at the position xa3π, xa3π where x is _______ . (Round off to the Nearest Integer) [a is an area as shown in the figure]

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EASY
The centre of mass of an extended body on the surface of the earth and its centre of gravity
HARD

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

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HARD

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Consider a uniform cubical box of side a on a rough floor that is to be moved by applying minimum possible force F at a point b above its centre of mass (see figure). If the coefficient of friction is μ=0.4 , the maximum possible value of 100×ba for a box not to topple before moving is ________

EASY
In a physical balance working on the principle of moments, when 5mg weight is placed on the left pan, the beam becomes horizontal. Both the empty pans of the balance are of equal mass. Which of the following statements is correct?
EASY

A uniform rod of length 200 cm and mass 500 g is balanced on a wedge placed at 40 cm mark. A mass of 2 kg is suspended from the rod at 20 cm and another unknown mass m is suspended from the rod at 160 cm mark as shown in the figure. Find the value of m such that the rod is in equilibrium. (g=10 m s-2

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MEDIUM

A bead of mass m stays at point Pa, b on a wire bent in the shape of a parabola y=Cx2 and rotating with angular speed ω (see figure). The value of ω is (neglect friction)

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