Explore topic-wise InterviewSolutions in Current Affairs.

True. 

The raindrop moves with terminal velocity due to viscous drag of the air. The terminal velocity of drop varies as the square of its radius. Hence, a bigger drop has a higher terminal velocity than a smaller one.

The full form of PVC is polyvinyl chloride. PVC is a thermoplastic. The plastics which gets deformed easily on heating and can be bent easily are called thermoplastics. It is used in the manufacturing of toys, combs and different types of containers.

The use of plastic has a bad effect on the environment because it is non biodegradable. It takes several years for plastic to decompose and it is not environment friendly. It causes environmental pollution. Also, the burning process of synthetic material is quite slow and it does not get completely burnt easily. It releases lots of poisonous fumes into the atmosphere when burned and causes air pollution.

The mirror is concave (since the focal length of concave mirror is taken as negative).

1. False 

2. True.

Modern healthcare would not be possible without the use of plastic materials. 

Plastics can be used in healthcare in the following ways:

1. Plastics are used in the packaging of tablets, syringes, doctor’s gloves and a number of medical instruments. 

2. Threads used for stitching wounds are made of medical instruments. 

3. Plastics are used for making intravenous blood bags and heart valves as well.

Plastic is non-biodegradable. It takes several years for plastic to decompose and it is not environment friendly. It causes environmental pollution. Also, the burning process of synthetic material is quite slow. It does not get completely burnt easily. It releases lots of poisonous fumes into the atmosphere when burned and causes air pollution.

The disposal of plastic wastes is a major problem because of the following reasons: 

1. Plastic is non-biodegradable. It takes several years for plastic to decompose and it is not environment-friendly. 

2. It causes environmental pollution. 

3. The disposal of plastic wastes is a major problem. Plastics cannot be burnt because they release poisonous gases. 

4. Plastic bags thrown in the garbage can be swallowed by the animals such as cows. It can result in choking their respiratory system and can be fatal. Therefore, we must avoid the use of plastic as much as possible.

Thermosetting plastics: The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. 

For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and Melamine is a thermosetting plastic which is resistant to fire and can tolerate heat better than other plastics. It is used to make floor tiles, kitchenware and fire resistant fabrics. It is used to make electrical switches and handles of utensils.

Thermoplastics: The plastics which gets deformed easily on heating and can be bent easily are called thermoplastics. 

For example, polythene and PVC are thermoplastics. These are used in the manufacturing of toys, combs and different types of containers.

Thermosetting plastics: The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. It is used to make electrical switches and handles of utensils. Melamine is a thermosetting plastic which is resistant to fire and can tolerate heat better than other plastics. It is used to make floor tiles, kitchenware and fire resistant fabrics.

The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. It is used to make electrical switches and handles of utensils. Melamine is a thermosetting plastic which is resistant to fire and can tolerate heat better than other plastics. Hence, electric witches, plugs and sockets made of thermosetting plastics.

Yes. I Touched a magnifying glass with my hand?

Flow rate is given by

R = πr²V_avg

R = 3.14 × (2 × 10^-3 )² × 0.983

⇒ R = 1.235 × 10^-5m³ /s

Therefore, the corresponding flow rate is 1.235 × 10^-5m³/s

a) Rate of evaporation increases with an increase of surface area. 

Explanation:

1. During evaporation process, the particles escape from the surface of liquid. 

2. The increase in the surface area provides more scope for particles to escape from the surface.

3. Hence it leads to increase the rate of evaporation.

Ex: Water in a China dish evaporates faster than the water in test tube.

b) Rate of evaporation decreases with the increase in humidity.

Explanation:

1. The amount of water present in air is called humidity. 

2. The air around us cannot hold more than a definite amount of water vapour at a given temperature.

3. If the amount of water vapour is high in air, then the rate of evaporation decreases. 

Ex : Clothes dry slowly on a rainy day than on a normal day.

c) Rate of evaporation increases with the increase in wind speed.

Explanation:

1. Because of increase in wind speed, particles of water vapour move away with the wind. 

2. Due to this, amount of water vapour in the surroundings decreases. 

3. It leads to increase in the rate of evaporation. 

Ex: Clothes dry faster on a windy day or under fan than a normal day.

Pressure = Force/area

= (1000N/10 x 10^-4M²) 

= 10⁶ Pa.

Data : h = 200 m, p = 1060 kg/m³ , p₀ = 1.013 × 10⁵ Pa, g = 9.8 m/s²

Absolute pressure, 

p = p₀ + hρg 

= (1.013 × 10³ ) + (200)(1060)(9.8) 

= (1.013 × 10⁵ ) + (20.776 × 10⁵ ) 

= 21.789 × 10⁵ = 2.1789 MPa

A material which gets decomposed through natural processes, such as action by bacteria, is called biodegradable. 

Following are the biodegradable materials:

Woollen clothes, paper, peels of vegetables and fruits, Cotton cloth and Jute bag.

A material which is not easily decomposed by natural processes is termed as non biodegradable. Following are the non-biodegradable materials:

Polythene bags, Aluminium cans, Toothbrush, Electric switch and Frying pan handle.

Plastic is non-biodegradable. It takes several years for plastic to decompose and it is not environment friendly. It causes environmental pollution. 

Following are the ways to save the environment from excessive plastic wastes:

1. We must try to Reduce, Reuse, Recycle and recover the use of plastic items. We must develop the habits which are environment friendly. 

2. We must not throw plastic in the water bodies or on the roads. 

3. We must take a cotton carry bag or a jute bag while shopping. 

4. We must try to minimize the use of plastic materials. 

For example, we must use a steel lunch box or steel containers instead of plastic ones.

Melamine and Bakelite are thermosetting plastics. The plastics which when moulded once, cannot be softened by heating are called thermosetting plastics. 

For example, Bakelite is a thermosetting plastic which is a poor conductor of heat and electricity. It is used to make electrical switches and handles of utensils. Melamine is a thermoseting plastic which is resistant to fire and can tolerate heat better than other plastics. It is used to make floor tiles, kitchenware and fire resistant fabrics.

Polythene and poly vinyl chloride are thermoplastics. The plastics which gets deformed easily on heating and can be bent easily are called thermoplastics. 

For example, polythene and PVC are thermoplastics. These are used in the manufacturing of toys, combs and different types of containers.

C) a virtual and magnified image

Unlike natural fibres, synthetic fibres are made from petroleum based chemicals or petrochemicals. Petrochemicals are subjected to various chemical processes to obtain synthetic fibres. Due to this they are called artificial fibres or synthetic fibres.

Pressure, p = \(\frac{F}A\) = \(\frac{200N}{10\times 10^{-6}m^2}\) = 2 x 10⁷ N/m²

(a) Plastic is non-biodegradable. It takes several years for plastic to decompose. When thrown in the water drains or in sewers it results in choking of the drains. Therefore, we must avoid the use of plastic as much as possible. 

(b) Plastic bags thrown in the garbage can be swallowed by the animals such as cows. It can result in choking their respiratory system and can be fatal. Therefore, we must avoid the use of plastic as much as possible.

Correct option is D) all

A) 0 < u < f

In response to a shear as well as normal force, a solid deforms and develops a restoring force. Within the elastic limit, both types of deformation is reversible. A solid changes its shape under a shear. A normal force causes a change in its length or volume. If the elastic limit is exceeded, the solid gets an irreversible deformation called a permanent set.

A fluid, on the other hand, can only be subjected to normal compressive stress, called pressure. A fluid does not have a definite shape, so that under a shear it begins to flow, Real fluids, with non-zero viscosity, display a weak resistance to shear.

Two non-SI units, which are either of historical interest, or are still used in specific fields are the bar and the torr. 

1 bar = 0.1 MPa = 100 kPa = 1000 hPa = 10⁵pa 

1 torr = (101325/760) Pa = 133.32 Pa 

[Note : Their use in modern scientific and technical work is strongly discouraged.]

An ideal fluid is one that has the following properties:

1. It is incompressible, i.e., its density has a constant value throughout the fluid. 

2. Its flow is irrotational, i.e., the flow is steady or laminar. In an irrotational flow, the fluid doesn’t rotate like in a whirlpool arid the velocity of the moving fluid at a specific point doesn’t change over time. (Many fluids change from laminar to turbulent flow as the speed of the fluid increases above some specific value. This can dramatically change the properties of the fluid.) 

3. Its flow is nonviscous or inviscid, i.e., internal friction or viscosity is zero so that no energy lost due the motion of the fluid.

A fluid is a substance that can flow. A fluid has shear modulus O and yields to shear. Under shear stress and a pressure gradient, fluid begins to flow. Liquids, gases, and plasmas are collectively called fluids.

Examples: All gases, all liquids, molten glass and lava, honey, etc.

Plastic containers are used as storage devices because

1. They are non-reactive: Metals like iron get rusted when they left exposed to moisture and air. But plastic do not react with water and air. So they are not corroded easily. 

2. Plastic is light, strong and durable: Plastics are very strong, light and durable can be moulded into different shapes. 

3. Lower price: Plastics have relatively lower price when compared with metals.

Plastic is a polymer like a synthetic fibre. The arrangement of units in a plastic can be linear or cross-linked. 

Plastic containers are preferred for storing food because of the following reasons:

• Plastic is non-reactive. It does not react with water and air. It is therefore, safe to keep food in plastic containers. 

• Plastic is light, strong and durable and can be moulded into different shapes and sizes. It is cheaper than metals. It is widely used in making household items including food containers. 

• Plastics are poor conductors of heat and electricity and can be used for making handles of frying pans.

Modulus of rigidity indicates resistance offered by solid to change in its shape.

Nylon has very high tensile strength. Nylon fibers are very strong. They are used for making ropes which are used for climbing rocks and for making parachutes.

As nylon is a very strong fibre, it is used for making parachutes, rock climbing ropes, fishing nets, seat belts. A nylon thread is actually stronger than steel wire.

The common defects of vision are 

i) Myopia 

ii) Hypermetropia 

iii) Presbyopia.

1. If focal length is increased, then power of lens decreases. 

2. If focal length is decreased, then power of lens increases.

Both A and R are true and R is not the correct explanation of A.

Iris helps in controlling the amount of light entering the eye through pupil.

1. It is the innermost delicate membrane having a large number of receptors called ‘rods’ and ‘cones’. 

2. The rods identify the colour and the cones identify the intensity of light. 

3. The retina is a part on which the image of an object is formed.

1. Optic nerve consists of a large number of fibres. 

2. These optic nerve fibres are connected to the rods and cones. 

3. Optic nerve fibers transmit the light signals to the brain.

Iris : 

The muscular diaphragm between the aqueous humour and the lens is called ‘iris’. Iris is the coloured part that we see in an eye. 

Pupil: 

The small hole in iris is called ‘pupil’.

It forms virtual, erect and magnified image.

The process of re-emission of light in all directions with different intensity is called scattering of light. The re-emitted light is called scattered light.

1. Iris consists of muscles which help in controlling the amount of light entering the eye through pupil. 

2. In case of low light the iris makes the pupil to expand and allow more light to enter the eye. 

3. In case of bright or excess light the iris makes the pupil to contract in order to decrease the amount of light entering the eye. The iris consists of muscles that expand and contract the pupil.

Power of lens is inversely proportional to its focal length.

P = 1/f (f in meters)

Given P = 2D

∴ f= 1/P = 1/2 = 0. 5 m = 50 cm.

The focal length positive indicates it is a convex lens.

f = - 20 cm = - 20/100 = -0.2 m ( Focal length of concave lens is negative)

P = 1/f (f in meter) = 1/ -0.2 = -5D

The power get halved.

For myopia the focal length = – far point distance = – 2m

Power = 1/f = 1/-2 = 0.5 D

The person is suffering from Myopia. The lens is concave and its focal length f = – 2m.

P = 1/5 = 1/-2 = -0.5D

So to correct the defect concave lens of 

– 0.5 D power should be used (b).