Physics Practice Questions

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Questions and Answers

A diver in a swimming pool bends his head before diving. It

Increases his moment of inertia

Increases his linear velocity

Decreases his moment of inertia (correct)

Decreases his angular velocity

The angular momentum of a system of particles is conserved

When axis of rotation remains the same

When no external torque acts upon the system (correct)

When no external force acts upon the system

When no external impulse acts upon the system

A stone is tied to one end of a string. Holding the other end, the string is whirled in a horizontal plane with progressively increasing speed. It breaks at some speed because

The required centripetal force is greater than the tension sustained by the string (correct)

The required centripetal force is lesser than the tension in the string

Gravitational forces of the earth is greater than the tension in string

The centripetal force is greater than the weight of the stone

The moment of inertia of a circular loop of radius R, at a distance of R/2 around a rotating axis parallel to horizontal diameter of the loop is

3/4 MR2 Signup and view all the answers

A 500 kg car takes a round turn of radius 50m with a velocity of 36 km/hr. The centripetal force is

1000N Signup and view all the answers

A cyclist riding a bicycle at a speed of 14√3 m/s takes a turn around a circular road of radius 20√3 m without skidding. Given g = 9.8 m/s², what is his inclination to the vertical

60° Signup and view all the answers

A string of length l fixed at one end carries a mass m at the other. The string makes 2/π revolutions/sec around the vertical axis through the fixed end.. The tension in the string is

16 ml Signup and view all the answers

Find the radius of gyration of a uniform disc about an axis perpendicular to its plane and passing through its center.

R/√2 Signup and view all the answers

Does the angle of banking depend on the mass of the vehicle?

False Signup and view all the answers

During ice ballet, while in the outer rounds, why do the dancers outstretch their arms and legs?

To increase their moment of inertia Signup and view all the answers

State the principle of conservation of angular momentum.

The total angular momentum of a system remains constant if no external torque acts on that system. Signup and view all the answers

Two bodies have their moments of inertia I and 2I respectively about their axis of rotation. If their kinetic energies of rotation are equal, then what is the ratio of their angular velocity?

1:√2 Signup and view all the answers

A hollow sphere has radius 6.4 m. what is the minimum velocity required by a motor cyclist at bottom to complete the circle.

17.7 m/s Signup and view all the answers

A bend in a level road has a radius of 100m. find the maximum speed which a car turning this bend may have without skidding, if the coefficient of friction between the tyres and road is 0.8.

28 m/s Signup and view all the answers

A flywheel is revolving with a constant angular velocity. A chip of its rim breaks and flies away. What will be the effect on its angular velocity?

The angular velocity will remain unchanged. Signup and view all the answers

The moment of inertia of a uniform circular disc about a tangent in its own plane is 5/4MR2 where M is the mass and R is the radius of the disc. Find its moment of inertia about an axis through its centre and perpendicular to its plane.

(1/2)MR² Signup and view all the answers

Derive an expression for maximum safety speed with which a vehicle should move along a curved horizontal road. State the significance of it.

The maximum safe speed (v) with which a vehicle can travel along a curved road without skidding is given by v = √(μRg), where μ is the coefficient of friction between the road and the tires, R is the radius of the curve, and g is the acceleration due to gravity. This is the maximum speed that the vehicle can maintain without exceeding the frictional force available between the tires and the road. Signup and view all the answers

The moment of inertia of a body about a given axis is 1.2 kgm². initially the body is at rest. For what duration on angular acceleration of 25 radian/sec² must be applied about that axis in order to produce a rotational kinetic energy of 1500 joule?

2 seconds Signup and view all the answers

A bucket containing water is tied to one end of a rope 5 m long and it is rotated in a vertical circle about the other end. Find the number of rotations per minute in order that the water in the bucket may not spill.

13.37 rpm Signup and view all the answers

A body weighing 0.5 kg tied to a string is projected with a velocity of 10 m/s. The body starts whirling in a vertical circle. If the radius of the circle is 0.8 m, find the tension in the string when the body is at the top of the circle.

3.8 N Signup and view all the answers

Derive an expression for kinetic energy of a rotating body with uniform angular velocity.

The kinetic energy (KE) of a rotating body with uniform angular velocity (ω) is given by KE = (1/2)Iω², where I is the moment of inertia of the body. Signup and view all the answers

Obtain an expression for the torque acting on a rotating body with constant angular acceleration.

The torque (τ) acting on a rotating body with constant angular acceleration (α) is given by τ = Iα, where I is the moment of inertia of the body. Signup and view all the answers

Derive an expression for the difference in tensions at highest and lowest point for a particle performing vertical circular motion.

The difference in tension (ΔT) between the highest and lowest points of a vertical circular motion of a particle is given by ΔT = 3mg, where m is the mass of the particle and g is the acceleration due to gravity. Signup and view all the answers

Obtain an expression for the angular momentum of a body rotating with uniform angular velocity.

The angular momentum (L) of a body rotating with uniform angular velocity (ω) is given by L = Iω, where I is the moment of inertia of the body. Signup and view all the answers

A railway track goes around a curve having a radius of curvature of 1 km. The distance between the rails is 1 m. Find the elevation of the outer rail above the inner rail so that there is no side pressure against the rails when a train goes round the curve at 36 km / hr.

1.02 cm Signup and view all the answers

A flywheel of mass 8 kg and radius 10 cm rotating with a uniform angular speed of 5 rad / sec about its axis of rotation, is subjected to an accelerating torque of 0.01 Nm for 10 seconds. Calculate the change in its angular momentum and change in its kinetic energy.

The change in angular momentum is 0.1 kgm²/s and the change in kinetic energy is 0.625 J. Signup and view all the answers

Two wheels of moment of inertia 4 kgm² rotate side by side at the rate of 120 rev / min and 240 rev / min respectively in the opposite directions. If now both the wheels are coupled by means of a weightless shaft so that both the wheels rotate with a common angular speed. Calculate the new speed of rotation.

60 rpm. Signup and view all the answers

State and explain the theorem of parallel axes.

The theorem of parallel axes states that the moment of inertia of a body about any axis is equal to the sum of the moment of inertia about a parallel axis passing through the center of mass of the body and the product of the mass of the body and the square of the distance between the two axes. Mathematically, I = Icm + Md², where I is the moment of inertia about the given axis, Icm is the moment of inertia about a parallel axis passing through the center of mass, M is the mass of the body, and d is the distance between the two axes. Signup and view all the answers

What is a conical pendulum? Obtain an expression for its time period.

A conical pendulum is a simple pendulum whose bob is allowed to move in a horizontal circle. The time period of a conical pendulum is given by T = 2π√(Lcosθ / g), where L is the length of the pendulum and θ is the angle the pendulum makes with the vertical. Signup and view all the answers

Obtain an expression for maximum safety speed with which a vehicle can be safely driven along a curved banked road

The maximum safe speed (v) a vehicle can travel along a curved banked road without skidding is given by v =√(Rg(tanθ + μ) / (1-μ tanθ)), where R is the radius of the curve, θ is the angle of banking, μ is the coefficient of friction between the tires and the toad, and g is the acceleration due to gravity. Signup and view all the answers

Show that the angle of banking is independent of mass of vehicle.

The angle of banking (θ) is given by tanθ = v²/Rg, where v is the speed of the vehicle, R is the radius of the curve, and g is the acceleration due to gravity. This expression does not include the mass of the vehicle, indicating that the angle of banking is independent of the vehicle's mass. Therefore, the banking angle can be optimized for a range of vehicle masses. Signup and view all the answers

Insect moves over surface of water because of

Surface tension Signup and view all the answers

The water droplets are spherical in free fall due to

Surface tension Signup and view all the answers

Surface tension of a liquid at critical temperature is

Zero Signup and view all the answers

Unit of coefficient of viscosity is

Ns/m² Signup and view all the answers

Study Notes

Question Bank - March 2021

Standard: 12th
Subject: Physics

Instructions

The questions are for practice only, and do not guarantee inclusion in the board exams.
Questions in this bank do not necessarily represent the complete range of possible exam questions.

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Description

This quiz contains a collection of practice questions for 12th-grade Physics. Designed to help students prepare for their board exams, these questions cover a variety of topics in physics. Keep in mind that these questions are for practice only and may not reflect the actual exam content.

Physics Practice Questions - 12th Standard

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