Newton's Second Law for Rotational Motion

Author:B M Sharma
JEE Advanced
IMPORTANT

Important Questions on Newton's Second Law for Rotational Motion

EASY
IMPORTANT

Uniform rod AB is hinged at end A in horizontal position as shown in the figure. The other end is connected to a block through a massless string as shown. The pulley is smooth and massless. Masses of block and rod is same and is equal to $m$. Then acceleration of block just after release from this position is
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HARD
IMPORTANT

Two blocks each of mass m are hanging from a stepped pulley by an inextensible light string which passes over a stepped pulley. The mass of the pulley is m and its radius of gyration is k. If the string does not slide on the pulley, find the accelerations of the blocks.
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HARD
IMPORTANT

A light rigid rod is connected rigidly with two identical particles each of mass m as shown. The free end of the rod is smoothly pivoted at O. The rod is released from rest from its horizontal position at t=0. Find:
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(i) angular acceleration of the rod, at t=0.

(ii) reaction offered by the pivot, at t=0.

MEDIUM
IMPORTANT

A disc of mass m and radius r is pivoted smoothly with a block of mass M. A force F1 acts on m and another force F2 acts on M. Assume that ground is smooth. Find the:
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(i) Linear acceleration of the disc.

(ii) angular acceleration of the disc.

HARD
IMPORTANT

A uniform rod AB of mass m=2 kg and length l=1.0 m is placed on a sharp support P such that a=0.4 m and b=0.6 m. A spring of force constant k=600 N m-1 is attached to end B as shown in figure. To keep the rod horizontal, its end A is tied with a thread such that the spring is elongated by 1 cm. Calculate reaction of support P when the thread is burnt.
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HARD
IMPORTANT

A wheel of radius r and moment of inertia I about its axis is fixed at the top of an inclined plane of inclination θ as shown in figure. A string is wrapped around the wheel and its free end supports a block of mass M which can slide on the plane. Initially, the wheel is rotating at a speed ω in a direction such that the block slides up the plane. How far will the block move before stopping?
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HARD
IMPORTANT

A uniform rod of mass m and length l can rotate in a vertical plane about a smooth horizontal axis hinged at point H. Find the force exerted by the hinge just after the rod is released from rest, from an initial horizontal position?
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MEDIUM
IMPORTANT

A uniform rod of mass m and length l can rotate in a vertical plane about a smooth horizontal axis hinged at point H.
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(a) Find angular acceleration α of the rod just after it is released from initial horizontal position from rest?

(b) Calculate the acceleration (tangential and radial) of point A at this moment.

HARD
IMPORTANT

A weightless rod of length l with a small load of mass m at the end is hinged at point A as shown and occupies a strictly vertical position, touching a block of mass M. A light jerk sets the system in motion. For what mass ratio M/m will the rod form an angle θ=π/6 with the horizontal at the moment of the separation from the block?

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HARD
IMPORTANT

A square plate ABCD of mass m and side l is suspended with the help of two ideal strings P and Q as shown. Determine the acceleration (in m/s2) of corner A of the square just at the moment the string Q is cut. g=10 m/s2

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HARD
IMPORTANT

A uniform rod AB of mass 2 kg is hinged at one end A. The rod is kept in the horizontal position by a massless string tied to point B. Find the reaction of the hinge (in N) on end A of the rod at the instant when string is cut. g=10 m/s2

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HARD
IMPORTANT

A uniform solid cylinder A, of mass m1, can freely rotate about a horizontal axis fixed to a mount B, of mass m2. A constant horizontal force F, is applied to the end K, of a light thread tightly wound on the cylinder. The friction between the mount and the supporting horizontal plane is assumed to be absent. Find: 

(a) the acceleration of the point K
(b) the kinetic energy of this system, t seconds after the beginning of motion. 

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HARD
IMPORTANT

Two identical discs of mass m and radius r are arranged, as shown in the figure. If α is the angular acceleration of the lower disc and acm is the linear acceleration of the centre of mass of the lower disc, then the relation between acmα and r is

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