NEETprep Bank NEET Physics Systems of Particles and Rotational Motion Questions Solved


A block of mass m moving at a velocity v collides with another block of mass 2m at rest. The lighter block comes to rest after collision. Find the coefficient of restitution.

(a) 12                                               (b) 1

(c) 13                                               (d) 14

From conservation of linear momentum we can see that velocity of 2m will become v2 after collision (as mass is doubled)

              

      Now,                             e=Relative velocity of separationRelative velocity of approach                                         =V/2V=12

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PMT - 2011

A small mass attached to a string rotates on a frictionless table top as shown. If the tension on the string is increased by pulling the string causing the radius of the circular motion to decrease by a factor of 2, the kinetic energy of the mass will

                              

(a) Increase by a factor of 4                                       (b) Decrease by a factor of 2

(c) Remain constant                                                   (d) Increase by a factor of 2 

(a)        K.E.=L22I              From angular momentum conservation about centre              L  constant              I=mr2              K.E.'=L22mr'2        r'=r2              K.E.'=4 K.E.              K.E. is increased by a factor of 4.

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Three point masses ,m, each are placed at the vertices of an equilateral triangle of side a. Moment of inertia of the system about an axis COD passing through a mass m at and lying in the plane of COA & perpendicu- lar to OA is A) 2 ma (C) ^ ma? 7 na

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A particle is moving in a circular orbit with constant speed. Select wrong alternate. (a) Its linear momentum is conserved (b) Its angular momentum is conserved (c) It is moving with variable velocity (d) It is moving with variable acceleration

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ABC is a right angled triangular plate of uniform thickness. The sides are such that AB> BC as shown in figure. I, I2 and I3 are moments of inertia about AB, BCand AC respectively Then, which of the following relation is correct? 3 2 (a) 2 13 (c) 13 < 12 < 11 (b) I2 > I1> I3 (d) I3 > 11> I2

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One solid sphere A and another hollow sphere B are of same mass and same outer radii. Their moment of inertia about their di- ameters are respectively lA and lg such that (A) IA9 (B) A le (C) Aa

M.O.I. of solid sphere:IA=25MR2M.O.I. of hollow spher:IB=23MR2 

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PMT - 1997
A couple produces NTSE 1995; CBSE PMT 1997; DCE 2004] (a) Purely linear motion (b) Purely rotational motion (c) Linear and rotational motion (d) No motion

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A particle of mass 1 kg is kept at (1m, 1m, 1m). The moment of inertia of this particle about z-axis would be

1.  1 kg-m2

2.  2 kg-m2

3.  3 kg-m2

4.  None of these

r=12+12      =2  mI=mr2 = 1×22             = 2kg-m2

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One quarter sector is cut from a uniform circular disc of radius R. This sector has mass M. It is made to rotate about a line perpendicular to its plane and passing through the centre of the original disc. Its moment of inertia about the axis of rotation is IIT-JEE (Screening) 2001] 4 90 8 (d) 2 MR2

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A wheel is rotating at the rate of 33 rev/min. If it comes to stop in 20 s. Then, the angular retardation will be (a) π rad (b) 11π rad /s2 11π 200 (c) rad/s2 )rad/s 200

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