Recent questions and answers in System of Particles and Rotational Motion

Which of the following statements are correct for a spherical body rolling without slipping on a rough horizontal ground at rest.

answered Apr 2 by drshiltrivedi

1 answer

The torque $\overrightarrow{z}$ on a body about a given point is found to be $ \overrightarrow{A} \times \overrightarrow{L}$ where $\overrightarrow {A}$ is a constant vector and $\overrightarrow{L}$ is angular momentum about that point . From this it follows that. 1) $\large\frac{dL}{dt}$ is perpendicular to $\overrightarrow {L}$ at all times 2) the component of $\overrightarrow {L}$ in the direction of $\overrightarrow{A}$ does not change with time. 3) the magnitude of $\overrightarrow {L}$ does not change with time. 4) $\overrightarrow {L}$ does not change with time. Which of the following is correct?

answered Mar 13, 2020 by lalitadeo1970

1 answer

A uniform circular disc of radius r is placed on a rough horizontal surface and given a linear $w_0$ as shown. The disc com,es to rest after moving some distance to the right. It follows that

answered Sep 4, 2018 by gopal.churu2010

2 answers

The motion of a sphere moving on a rough horizontal surface change from pure sliding (without rolling) to pure rolling (with out slipping) . In this process, the force of friction. 1) initially acts opposite to the direction of motion and later in the direction of motion. 2) causes linear retardation 3) causes angular acceleration 4) stops acting when pure rolling begins. Which of the following is correct?

answered Apr 25, 2018 by blsaketh33

1 answer

A solid sphere of mass m is lying at rest on a rough horizontal surface. The coefficient of friction between the ground and sphere is $\mu$. The maximum value of F, so that the sphere will not slip is equal to

answered Apr 19, 2018 by jainnanu010

2 answers

A spherical body of radius R rolls on a horizontal surface with linear velocity $V$. Let $L_1$ and $L_2$ be the magnitude of angular momentum of the body about the centre of mass and point of contact P respectively. a) $L_2=L_1$ if radius of gyration $k=R$ b) $L_2=2L_1$ for all cases. c) $L_2 > 2L_1$ if radius of gyration $K < R$ d) $L_1> L_2$ if radius of gyration $ K > R$ Which of the following is correct?

answered Apr 9, 2018 by kingsumit011

1 answer

A man spinning in free space changes of his body e.g by spreading his arms and curling up. By doing this, he can change his 1) moment of inertia 2) angular momentum 3) angular velocity 4) rotational kinetic energy in this Which of the following is correct?

answered Feb 28, 2018 by priyanka.c

2 answers

A horizontal disc rotates freely about a vertical axis through its centre. A ring, having the same mass and radius as the disc , is now gently placed on the disc. After some time, the two rotate with a common angular velocity. 1) some friction exits between the disc and the ring 2) the angular mometum of disc plus ring is conserved. 3) the final common angular velocity is $\large\frac{2}{3}$ rd of the initial angular velocity of disc. 4) $\large\frac{2}{3}$ rd of the initial kinetic energy is converted to heat. Which of the following is correct?

answered Oct 8, 2017 by vlalithambica

1 answer

Two identical ladders are arranged as shown in the figure, resting on a horizontal surface. Mass of each ladder is M and length L. A block of mass m hangs from the apex point P. If the system is in equilibrium, find direction and magnitude of friction force acting at A or B.

answered Apr 1, 2016 by vijayalakshmi.r

1 answer

A particle of mass m is travelling with a constant velocity $\overrightarrow {V} =V_0 \hat i$ along the line $y=b,z=0$. Let $dA$ be the area swept out by the position vector from the origin to the particle in time at end L be the magnitude of angular momentum of particle about orgin at any time t. Then 1) L= constant 2) $\large\frac{dA}{dt}=\frac{L}{m}$ 3) $\large\frac{dA}{dt}= \frac{2L}{m}$ 4) $\large\frac{dA}{dt}=\frac{L}{2m}$ Which of the following is correct?

answered Apr 1, 2016 by vijayalakshmi.r

1 answer

A string wrapped around a solid cylinder of mass M and radius R. The string is pulled vertically upward to prevent the centre of mass of the cylinder from falling as the cylinder unwinds the string. Choose the correct options: (A). the tension in the string is 2Mg (B). the length of the string unwound until its angular velocity becomes w is w^2R^2/2g (C).the angular acceleration of the cylinder is 2g/3R (D).work done by tension on the cylinder until its angular velocity becomes w is 1/4Mw^2R^2

asked Mar 27, 2015 by agarwal795

0 answers

Half of the uniform rectangular plate of length 'L' is made of material of density $d_1$and the other half of density $d_2$. The horizontal distance of center of mass from AB is

answered Mar 24, 2014 by meena.p

1 answer

A hollow sphere of radius R rests on a surface of finite coefficient of friction, A point object of mass m moved horizontally and his the sphere at a height of $\large\frac{R}{2}$ above its centre. The collision is completely inelastic. Which of the following is/are correct ? 1) total linear momentum of the system is not conserved 2) total angular momentum about centre of mass of the system remains constant. 3) the sphere gets finite angular velocity immediately after collision. 4) the sphere moves with finite speed immediately after collision.

asked Dec 9, 2013 by meena.p

0 answers

A ring without slipping on a horizontal surface. At any instant , its position is as shown in figure. 1) Section ABC has greater kinetic energy than ADC 2) Secion BC has same kinetic energy as section DA 3) Secion BC has greater kinetic energy than section DA 4) the Secion AB,BC,CD and DA have same kinetic energy Which of the following is correct?

asked Dec 9, 2013 by meena.p

0 answers

A ring rolls without slipping on the ground. Its centre C moves with a constant speed u. P is any point on the ring. The speed of P with respect to the ground is V. 1) $0 \leq v \leq 2u$ 2) $v=u $, if CP horizontal 3) $v=u$ if CP makes an angle of $60^{\circ}$ with the horizontal and p is below the horizontal level of C 4) $v= \sqrt 2 u$ if CP is horizontal Which of the following is correct?

asked Dec 9, 2013 by meena.p

0 answers

A thin uniform rod of mass m and length l is rotate about its upper end. When it is at rest, it receives an impulse J at its lowest point normal to its length. Immediately after impact, 1) the angular mometum of the rod is $JL$ 2) the angular velocity of the rod is $\large\frac{3J}{ml}$ 3) the kinetic energy of the rod is $\large\frac{3J^2}{2m}$ 4) the linear velocity of the midpoint of the rod is $\large\frac{3J}{3m}$ Which of the following is correct?

asked Dec 9, 2013 by meena.p

0 answers

Two identical spheres A and B are free to move and to rotate about their centres. They are given the same impacts J. The line of action of the impulses pass through the centre of A and away from the centre of B.

asked Dec 9, 2013 by meena.p

0 answers

A constant external torque acts for a very brief $\Delta t$ on a rotating system having moment of inertia I.

asked Dec 8, 2013 by meena.p

0 answers

Two horizontal discs of different radius are free to rotate about their central vertical axes. One is given some angular velocity, the other is stationary . Their rims are now brought in contact. There is friction between the rims.

asked Dec 8, 2013 by meena.p

0 answers

A body is in equilibrium under the influence of a number of a forces. Each force has a different line of action. The minimum number of forces required is

asked Dec 8, 2013 by meena.p

0 answers

When slightly different weights are placed on the two pane of a beam balance, the beam comes to rest at an angle with the horizontal. The beam is supported at a single point P by a pivot.

asked Dec 8, 2013 by meena.p

0 answers