Recent questions in 11th Physics

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Two particles, each of mass m and speed v, travel in opposite directions along parallel lines separated by a distance d. Show that the vector angular momentum of the two particle system is the same whatever be the point about which the angular momentum is

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A non-uniform bar of weight W is suspended at rest by two strings of negligible weight as shown in Fig.. The angles made by the strings with the vertical are 36.9° and 53.1° respectively. The bar is 2 m long. Calculate the distance d of the centre of gravity of the bar from its left end.

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A car weighs 1800 kg. The distance between its front and back axles is 1.8 m. Its centre of gravity is 1.05 m behind the front axle. Determine the force exerted by the level ground on each front wheel and each back

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) Find the moment of inertia of a sphere about a tangent to the sphere, given the moment of inertia of the sphere about any of its diameters to be 2M`R^2`/5, where M is the mass of the sphere and R is the radius of the sphere. (b) Given the moment of inertia of a disc of mass M and radius R about any of its diameters to be M`R^2`/4, find its moment of inertia about an axis normal to the disc and passing through a point on its

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Torques of equal magnitude are applied to a hollow cylinder and a solid sphere, both having the same mass and radius. The cylinder is free to rotate about its standard axis of symmetry, and the sphere is free to rotate about an axis passing through its centre. Which of the two will acquire a greater angular speed after a given

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A solid cylinder of mass 20 kg rotates about its axis with angular speed 100 rad `s^(-1)`. The radius of the cylinder is 0.25 m. What is the kinetic energy associated with the rotation of the cylinder? What is the magnitude of angular momentum of the cylinder about its

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) A child stands at the center 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

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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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 ? Assume that there is no

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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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%

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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From a uniform disk of radius R, a circular hole 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 gravity of the resulting flat

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A metre stick is balanced on a knife edge at its centre. When two coins, each of mass 5 g are put one on top of the other at the 12.0 cm mark, the stick is found to be balanced at 45.0 cm. What is the mass of the metre

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A solid sphere rolls down two different inclined planes of the same heights but different angles of inclination. (a) Will it reach the bottom with the same speed in each case? (b) Will it take longer to roll down one plane than the other? (c) If so, which one and

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A hoop of radius 2 m weighs 100 kg. It rolls along a horizontal floor so that its centre of mass has a speed of 20 cm/s. How much work has to be done to stop

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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The oxygen molecule has a mass of `5.30 × 10^(-26)` kg and a moment of inertia of `1.94×10^(-46)` kg `m^2` about an axis through its centre perpendicular to the lines joining the two atoms. Suppose the mean speed of such a molecule in a gas is 500 m/s and that its kinetic energy of rotation is two thirds of its kinetic energy of translation. Find the average angular velocity of the

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A solid cylinder rolls up an inclined plane of angle of inclination 30°. At the bottom of the inclined plane the centre of mass of the cylinder has a speed of 5 m/s. (a) How far will the cylinder go up the plane? (b) How long will it take to return to the

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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As shown in Fig., the two sides of a step ladder BA and CA are 1.6 m long and hinged at A. A rope DE, 0.5 m is tied half way up. A weight 40 kg is suspended from a point F, 1.2 m from B along the ladder BA. Assuming the floor to be friction-less and neglecting the weight of the ladder, find the tension in the rope and forces exerted by the floor on the ladder. (Take g = 9.8 m/`s^2`) (Hint: Consider the equilibrium of each side of the ladder separately.)

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A man stands on a rotating platform, with his arms stretched horizontally holding a 5 kg 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. The moment of inertia of the man together with the platform may be taken to be constant and equal to 7.6 kg `m^2`. (a) What is his new angular speed? (Neglect friction.) (b) Is kinetic energy conserved in the process? If not, from where does

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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A bullet of mass 10 g and speed 500 m/s is fired into a door and gets embedded exactly at the centre 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. (Hint: The moment of inertia of the door about the vertical axis at one end is

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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Two discs of moments of inertia `I_1` and `I_2` about their respective axes (normal to the disc and passing through the centre), and rotating with angular speeds `ω_1` and `ω_2` are brought into contact face to face with their axes of rotation coincident. (a) What is the angular speed of the two-disc system? (b) Show that the kinetic energy of the combined system is less than the sum of the initial kinetic energies of the two discs. How do you account for this loss in energy? Take `ω_1` ≠

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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(a) Prove the theorem of perpendicular axes. (Hint : Square of the distance of a point (x, y) in the x–y plane from an axis through the origin and perpendicular to the plane is `x^2+y^2`). (b) Prove the theorem of parallel axes. (Hint : If the centre of mass is chosen to be the origin `m_ir_i = 0`

asked Mar 19, 2022 in 11th Physics by varun (6.7k points)

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