EASY
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Differentiate between centre of mass and centre of gravity.

Important Questions on Laws of Motion

MEDIUM

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

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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

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
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 _____ .
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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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 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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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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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 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 :
EASY
The centre of mass of an extended body on the surface of the earth and its centre of gravity
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

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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EASY
Mechanical advantage (MA),  Load (L) and effort (E) are related as :
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

Two planets of radii r1and r2 are made from the same material having same density. The ratio of acceleration due to gravity g1g2 at the surfaces of the planets is

HARD

Gravitational force is essentially required for

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