Standard Books Physics Work, Energy and Power Class 11 Questions

The work-energy theorem states that the change in

A raindrop of mass 1 g falling from a height of 1 km hits the ground with a speed of 50 m s⁻¹. If the resistive force is proportional to the speed of the drop, then the work done by the resistive force is (Take g = 10 m s⁻²)

A body of mass 4 kg is moving with momentum of 8 kg m s⁻¹. A force of 0.2 N acts on it in the direction of motion of the body for 10 s. The increase in kinetic energy is

An object of mass m is released from rest from the top of a smooth inclined plane of height h. Its speed at the bottom of the plane is proportional to

A body is being raised to a height h from the surface of earth. What is the sign of work done by applied force and gravitational force respectively?

A body constrained to move along y-axis is subjected to a constant force F = -î + 2ĵ + 3k̂ N. The work done by this force in moving the body a distance of 4 m along y-axis is

A particle acted upon by constant forces 4î + ĵ - 3k̂ and 3î + ĵ - k̂ is displaced from the point î + 2ĵ + 3k̂ to point 5î + 4ĵ + k̂. The total work done by the forces in SI unit is

How much mass has to be converted into energy to produce electric power of 500 MW for one hour?

A uniform chain of length 2 m is kept on a table such that a length of 60 cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. The work done in pulling the entire chain on the table (Take g = 10⁻²)

A uniform chain of length L and mass M is lying on a smooth table and one third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, work required to pull the hanging part on to the table is

A block of mass 2 kg initially at rest moves under the action of an applied horizontal force of 6 N on a rough horizontal surface. The coefficient of friction between block and surface is 0.1. The work done by the applied force in 10 s is (Take g = 10 m s⁻²)

In the previous question, the work done by friction in 10 s is

If the force acting on a body is inversely proportional to its speed, then its kinetic energy is

A truck and a car moving with the same kinetic energy are brought to rest by the application of brakes which provide equal retarding forces. Which of them will come to rest in a shorter distance?

The momentum of a body is increased by 25%. The kinetic energy is increased by about

In a ballistics demonstration a police officer fires a bullet of mass 50 g with speed 200 m s⁻¹ on soft plywood of thickness 2 cm. The bullet emerges with only 10% of its initial kinetic energy. The emergent speed of the bullet is

Two bodies A and B have masses 20 kg and 5 kg respectively. Each one is acted upon by a force of 4 kg wt. If they acquire the same kinetic energy in times tₐ and tᵦ, then the ratio tₐ/tᵦ is

The area under force-displacement curve represents

A force F acting on an object varies with distance x as shown in the figure. The work done by the force in moving the object from x = 0 to x = 20 m is

A force F acting on an object varies with distance x as shown in the figure. The work done by the force in moving the object from x = 0 to x = 8 m is

A block of mass 10 kg is moving in x-direction with a constant speed of 10 m s⁻¹. It is subjected to a retarding force Fᵣ = -0.1 x J m⁻¹ during its travel from x = 20 m to x = 30 m. Its final kinetic energy will be

The potential energy of a system increases if work is done

The negative of the work done by the conservative internal forces on a system equals to the change in

Which one of the following is not a conservative force?

Identify the false statement from the following.

Which of the following statements is incorrect?

A ball bounces to 80% of its original height. What fraction of its potential energy is lost in each bounce?

The potential energy of a spring when stretched through a distance x is 10 J. What is the amount of work done on the same spring to stretch it through an additional distance x?

A bullet of mass m moving horizontally with a velocity v strikes a block of wood of mass M and gets embedded in the block. The block is suspended from the ceiling by a massless string. The height to which block rises is

A ball of mass m is dropped from a cliff of height H. The ratio of its kinetic energy to the potential energy when it is fallen through a height 3/4 H is

When a long spring is stretched by 2 cm, its potential energy is U. If the spring is stretched by 10 cm, the potential energy in it will be

A car of mass 1000 kg moving with a speed 18 km h⁻¹ on a smooth road collides with a horizontally mounted spring of spring constant 6.25 × 10³ N m⁻¹. The maximum compression of the spring is

A block of mass 2 kg is dropped from a height of 40 cm on a spring whose force-constant is 1960 N m⁻¹. The maximum distance through which the spring is compressed by

A crane lifts a mass of 100 kg to a height of 10 m in 20 s. The power of the crane is (Take g = 10 m s⁻²)

A force (4î + ĵ - 2k̂) N acting on a body maintains its velocity at (2î + 2ĵ + 3k̂) m s⁻¹. The power exerted is

A body is initially at rest. It undergoes one dimensional motion with constant acceleration. The power delivered to it at time t is proportional to

An elevator which can carry a maximum load of 1800 kg (elevator + passengers) is moving up with a constant speed of 2 m s⁻¹. The frictional force opposing the motion is 4000 N. What is minimum power delivered by the motor to the elevator?

A pump on the ground floor of a building can pump up water to fill a tank of volume 30 m³ in 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%, how much electric power is consumed by the pump? (Take g = 10 m s⁻²)

A bicyclist comes to a skidding stop in 10 m. During this process, the force on the bicycle due to the road is 200 N and is directly opposed to the motion. The work done by the cycle on the road is

Assertion: The work done by the spring force in a cyclic process is zero. Reason: Spring force is a conservative force.

A cord of negligible mass is wound round the rim of a flywheel of mass 20 kg and radius 20 cm. A steady pull of 25 N is applied on the cord. The work done by the pull when 2 m of the cord is unwound is

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⁻¹. How much work has to be done to stop it?