Question Answers
Sahay Sir > Question Answers
A bullet of mass 10 g and speed 500 m/s is fired into a door and gets embedded exactly at the center of the door. The door is 1.0 m wide and weighs 12 kg. It is hinged at one end and rotates about a vertical axis practically without friction. Find the angular speed of the door just after the bullet embeds into it.
27
Nov
A bullet of mass 10 g and speed 500 m/s is fired into a door and gets embedded exactly at the center of the door. The door is 1.0 m wide and weighs 12 kg. It is hinged at one end and rotates about a vertical axis practically without friction. Find the angular speed of [...]
A man stands on a rotating platform, with his arms stretched horizontal holding a 5kg weight in each hand. The angular speed of the platform is 30 revolutions per minute. The man then brings his arms close to his body with the distance of each weight from the axis changing from 90cm to 20cm. moment of inertia of the man together with the platform may be taken to be constant and equal t 7.6kgm2. (a) What is the his new angular speed ? (Neglect friction.) (b) Is kinetic energy conserved in the process ? If not, from where does the change come about ?
27
Nov
A man stands on a rotating platform, with his arms stretched horizontal holding a 5kg weight in each hand. The angular speed of the platform is 30 revolutions per minute. The man then brings his arms close to his body with the distance of each weight from the axis changing from 90cm to 20cm. moment [...]
Posted in:
Chapter 6 - System of Particles and Rotational Motion
,
NCERT Exemplar Class 11
,
Physics
,
Tags:
A man stands on a rotating platform ,
an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice ,
applied torque is needed to counter frictional torque). Assume that the engine is 100% efficient. ,
To maintain a rotor at a uniform angular speed of 200 rad s^−1 ,
A sphere rolls up an inclined plane whose inclination is 30^∘. At the bottom of the inclined plane, the center of mass of the sphere has a translational speed of 5ms^−1 (a) How far does the sphere travel up the plane? (b) How long does it take to return to the bottom?
27
Nov
A sphere rolls up an inclined plane whose inclination is 30^∘. At the bottom of the inclined plane, the center of mass of the sphere has a translational speed of 5ms^−1 (a) How far does the sphere travel up the plane? (b) How long does it take to return to the bottom? A sphere rolls [...]
The oxygen molecule has a mass of 5.30×10^−26kg and a moment of inertia of 1.94×10^−46kgm^2 about an axis through its centre perpendicular to the line joining the two atoms. Suppose the mean speed of such a molecule in a gas is 500m/s and that its kinetic energy of rotation is two/thirds of its kinetic energy of translation. Find the average angular velocity of the molecule.
27
Nov
The oxygen molecule has a mass of 5.30×10^−26kg and a moment of inertia of 1.94×10^−46kgm^2 about an axis through its centre perpendicular to the line joining the two atoms. Suppose the mean speed of such a molecule in a gas is 500m/s and that its kinetic energy of rotation is two/thirds of its kinetic energy [...]
Posted in:
Chapter 6 - System of Particles and Rotational Motion
,
NCERT Exemplar Class 11
,
Physics
,
Tags:
an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice ,
applied torque is needed to counter frictional torque). Assume that the engine is 100% efficient. ,
To maintain a rotor at a uniform angular speed of 200 rad s^−1 ,
A hoop of radius 2m weight 100kg. It rolls along a horizontal floor so that its centre of mass has a speed of 20cms^−1. How much work has to be done to stop it ?
27
Nov
A hoop of radius 2m weight 100kg. It rolls along a horizontal floor so that its centre of mass has a speed of 20cms^−1. How much work has to be done to stop it ? A hoop of radius 2m weight 100kg. It rolls along a horizontal floor so that its centre of mass has [...]
From a uniform disc of radius R, a circular section of radius R/2 is cut out. The centre of the hole is at R/2 from the centre of the original disc. Locate the centre of mass of the resulting flat body.
27
Nov
From a uniform disc of radius R, a circular section of radius R/2 is cut out. The centre of the hole is at R/2 from the centre of the original disc. Locate the centre of mass of the resulting flat body. a circular section of radius R/2 is cut out. The centre of the hole [...]
Consider the sphere moving on a horizontal surface. At some instant it has linear velocity v0 and angular velocity about the centre of mass v0/2R. The translational velocity after the sphere starts pure rolling
27
Nov
Consider the sphere moving on a horizontal surface. At some instant it has linear velocity v0 and angular velocity about the centre of mass v0/2R. The translational velocity after the sphere starts pure rolling A ball rests upon a flat piece of paper on a table top. The paper is pulled horizontally but quickly towards [...]
Tags:
A ball rests upon a flat piece of paper on a table top. The paper is pulled horizontally but quickly towards right as shown. Relative to its initial position with respect to the table ,
i.e. in the direction in which the paper is pulled. Here ,
i.e. to the left if there is a friction between the paper and the ball. c) moves forward ,
the ball a) remains stationary if there is no friction between the paper and the ball. b) moves to the left and starts rolling backwards ,
the correct statement/s is /are.......... ,
To maintain a rotor at a uniform angular speed of 200 rad s^−1 , an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice, applied torque is needed to counter frictional torque). Assume that the engine is 100% efficient.
27
Nov
To maintain a rotor at a uniform angular speed of 200 rad s^−1 , an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice, applied torque is needed to counter frictional [...]
Posted in:
Chapter 6 - System of Particles and Rotational Motion
,
NCERT Exemplar Class 11
,
Physics
,
Tags:
an engine needs to transmit a torque of 180 N m. What is the power required by the engine ? (Note: uniform angular velocity in the absence of friction implies zero torque. In practice ,
applied torque is needed to counter frictional torque). Assume that the engine is 100% efficient. ,
To maintain a rotor at a uniform angular speed of 200 rad s^−1 ,
A rope of negligible mass is wound round a hollow cylinder of mass 3 kg and radius 40 cm. What is the angular acceleration of the cylinder if the rope is pulled with a force of 30 N? What is the linear acceleration of the rope ? Assuming that there is no slipping.
27
Nov
A rope of negligible mass is wound round a hollow cylinder of mass 3 kg and radius 40 cm. What is the angular acceleration of the cylinder if the rope is pulled with a force of 30 N? What is the linear acceleration of the rope ? Assuming that there is no slipping. find its [...]
(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to 2/5 times the initial value ? Assume that the turntable rotates without friction. (b) Show that the child’s new kinetic energy of rotation is more than the initial kinetic energy of rotation. How do you account for this increase in kinetic energy?
27
Nov
(a) A child stands at the centre of a turntable with his two arms outstretched. The turntable is set rotating with an angular speed of 40 rev/min. How much is the angular speed of the child if he folds his hands back and thereby reduces his moment of inertia to 2/5 times the initial value [...]