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(i) London was a city of clerks and shopkeepers. 

(ii) It was a city of small masters and skilled artisans. 

(iii) It was a city of growing number of semi skilled and sweated out workers, of soldiers and servants, of casual labourers, street sellers and beggars.

(iv) Apart from the London dockyards, five major types of industries that employed large number of people were : Clothing and footwear, wood and furniture, metals and engineering, printing and stationery and precision products such as surgical instruments, watches and objects of precious metal. 

(v) During the Fire World War. London began manufacturing motor care and electrical goods and the number of large factories increased until they accounted for nearly one- third of all jobs in the city.

twentieth century were primarily based on industrial and technological advancements. Consequently, women had to work in households for a living, and this led to an increase in the number of domestic servants. Some women also began to earn by lodging out rooms, tailoring, washing or making matchboxes. With the coming of the First World War though, women once again joined the industrial sector.

When the object falls its potential energy becomes zero when it reaches at ground level. So, change in potential energy is equal to potential energy when the object is at full height as in question.

Mass = 6 kg, h = 5 m

PE = mgh

= 6 kg x 10 ms^-2 x 5 ms 

= 300 J

Here mass = 40 kg, h = 10 m and g = 9.8 m/s²

Work done can be calculated as follows:

W = F.s = mgh

W = 40 kg x 9.8 ms^-2 x 10

m = 3920 J = 3.92 kJ

Correct answer is (a) mgh

Correct answer is (d) 1/2 mv²

During conversion of energy from one form to another, all of energy does not get converted into one form of energy rather some of the energy is dissipated in the form of heat, light and sound energy. For example; when a ceiling fan is switched on, electrical energy is converted into kinetic energy. During this change, some of the energy is converted into heat energy which is evident from ceiling fan becoming hot. 

Following steps can be taken to reduce dissipation of energy: 

• The machine should be subjected to continuous maintenance and timely repair. 
• Lubricants should be used in machine. 
• More efficient machines should be designed, e.g. a car with better mileage. 
• Electrical appliances of higher star rating should be used.

(a) The energy in charged particles is called electrical energy. Flow of water is used for moving the turbine. Turbine converts kinetic energy into electric energy. 

(b) Blades of windmill move due to wind speed. Fan of windmill is attached to a turbine. Turbine converts kinetic energy into electric energy. 

(c) Solar energy plant uses two methods to produce electricity. In one method, photovoltaic cells convert heat energy into electric energy. In another method, water is converted into steam by using heat energy. Steam is then utilized to turn the turbines and electricity is produced.

(b) By boiling water to produce steam

It is a panel on which many solar cells are installed, which convert Sun’s energy into electrical energy. 

Two advantages: Solar cell panels can be setup at remote places and secondly it has no moving parts, require less maintenance and work quite satisfactorily without the use of any focusing device.

(c) By running dynamo by kinetic energy of water

In hydel power plant, water is stored behind a dam. After that, water is released thorough sluice gates. The flow of water facilitated the movement in turbine. While doing so, kinetic energy of turbine is converted into electric energy.

The energy in a charged object is called electric energy. In a thermal power plant, fuel is burnt to convert water into steam. The steam is then channelized to propellers of turbine, The flow of steam facilitates the movement in turbine. While doing so, kinetic energy of turbine is converted into electric energy.

In order to produce hydroelectricity, high rise dams are constructed on the river to obstruct the flow of water and thereby collect water in very large reservoirs. The water from high level in the dam is carried through pipes, to the turbine, at the bottom of the dam. The turbines are connected to the generator. Rotation of the turbines makes the generator produce electricity. Water when stored at a height in the dam has a large amount of potential energy which gets converted into the kinetic energy of flowing water when it is allowed to fall on the turbines it gets converted into mechanical energy of the turbine and finally gets converted into the electric energy by the generator.

Zero, because gravitational force is a conservative force and act perpendicular to direction of motion of moon.

Work done is zero since force and displacement are in perpendicular direction, 

i.e. w = 0.

(i) Kinetic energy is the energy present in a body by virtue of its motion. When water is stored in a dam at particular height, we say it has maximum potential energy as the water is present at a height. When this water is allowed to fall down from a certain height, it is said to have kinetic energy. When the water falls on a turbine, the paddle wheels rotates to rotate the turbine. Hence the kinetic energy of water is used to push or rotate the turbine which is further used to produce the electricity. 

(ii) Potential energy present in a body is due to virtue of its position. In hydel power plant, the kinetic energy of water to rotate the turbine is obtained by the use of potential energy of water stored in dam. When water is stored in dam at a certain height, potential energy is stored in the water which transforms into kinetic energy when it released from that height.

(a) An object has some mass ‘M, when it is raised through a certain height, energy is applied on it, this energy gets transformed and is gained by the object hence its potential energy increases. 

(b) Energy is present in every object in some or other form. It exist in sun, planet, wind, water etc, the energy gets transformed and we get, because of its transformation into different form. For e.g., sun energy → plants convert it (due to chemical reaction) into food energy → we eat green vegetables products of plants, energy enters our body

(c) Work is said to be done, when force is applied on the body and it moves to certain distance. When a wall is pushed there is no displacement and we say that work done is zero.

No.

A car exerts some force on the road and road exerts same force on the car but displacement of road is zero so work done by road is zero.

1 kWh = 1 kW x 1 h 

= 1000 W x 3600 s 

= 3600000J 

= 3.6 x 106J

1 kWh = 1000 × 3600 Ws = 3.6 × 10⁶ J.

Correct answer is  (a) energy

The term work is used in diverse contexts in daily life. It refers to both physical as well as mental work. In fact, any activity can generally be called as work. But in Physics, the.term work is treated as a physical quantity with a precise definition. Work is said to be done by the force when the force applied on a body displaces it.

Correct answer is (b) \(\frac{3}{2} k\)

At maximum compression x_m , the K.E. of the car is converted entirely into the P.E. of the spring.

∴ \(\frac{1}{2} kx^2_m\) = \(\frac{1}{2} mv^2\) or \(x_m\) = 2m.

Increases because W.D. on it when it increases is compressed or stretched.

Force constant of each half becomes twice the force constant of the original spring.

It is the restoring force set up in a string per unit extension.

Whenever a mass collides and sticks to other mass, the nature of collision is inelastic.

P.E. of spring when stretched through a distance 01m,

U = W.D = \(\frac{1}{2}\)Kx² = 20J

K = 4000 N/m

when spring is further stretched through 01m, then P.E. will be :

U' = \(\frac{1}{2}\) K(0.2)² = 80J

∴ W.D = U' -U = 80-20 = 60J.

(b) negative

Correct answer is (a) 10^-7 J