IITJEE PHYSICS: Mechanics

Mulitiple choice question with one or more answer


1. The motion of center of mass of a system of two particles is unaffected by their internal forces
a, irrespective of the actual direction of the internal forces
b,only if they are along the line joining the particles
c.only if they are obliquely inclined to the line joinng the particles
d. only if they are right angles to the line joining the particles



2.Two discs of moments of inertia I1 and I2 about their respective axis rotating with angular frequencies ω1 and ω2 respectively are brought into contact face to face with their axes of rotation coincident.Which of the following is true
a.The angular frequency of the composite disc is (I1ω1+I2ω2)/(I1+I2)
b.dL/dt is constant for the system
c.Moment of the inertia of the composite disc about the axis is I1+I2
d. None of these



3.Net force on a system of particles is zero from some interial frame.which of the following is correct
a.Center of mass acceleration is zero from that inertial frame
b. Net momentum is constant from that frame
c.Net momentum from the frame of Center of mass is zero and constant
d. KE of the system from center of mass frame may be constant



4.Three points masses each of mass m are placed at the corner of an equilateral triangle of side a.The moment of inertia of the system about an axis along one side of an triangle is
a.3ma2/4
b. ma2/4
c. ma2/2
d ma2/6




5. A solid sphere rolls without slipping with speed v and presses a spring of spring constant k.The compression in the spring will be
a.(2Mv2/3k)1/2
b.(2Mv2/5k)1/2
c.(5kv2/7M)1/2
d.(7Mv2/5k)1/2

6.A solid cylinder of mass M and radius R is being pulled along a horizontal surface on which its perform pure rolling by a horizontal force F applied at its center.which of the following is true
a.Angular acceleration of the cylinder about the axis passing through center of mass is 2F/3MR
b.Frictional force acting on the cylinder is F/3
c.Velocity of a point on the top of cylinder after 3 sec is 4P/M
d . None of these



7.A uniform chain of mass M and lenght L is held on a horizontal frictionless table with 1/k lenght hanging over the edge of the table.The workdone in pulling the chain up the table
a.MgL/k
b. MgL/2k
c. MgL/k2
d. MgL/2k2



Solutions

1.Ans a
2.Ans a,b,c
3.ans a,b,c,d
4.aNS A
6.ans a,b,c
7.ans d

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