A boat will float when the weight of the water it displaces equals the weight of the boat and anything will float if it is shaped to displace its own weight of water before it reaches the point where it will submerge. Floating of the boat works on the principle of buoyancy force which is an upward force exerted by a liquid, gas or other fluid, that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards.

Correct Option: B

A boat will float when the weight of the water it displaces equals the weight of the boat and anything will float if it is shaped to displace its own weight of water before it reaches the point where it will submerge. Floating of the boat works on the principle of buoyancy force which is an upward force exerted by a liquid, gas or other fluid, that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards.

Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface.

Correct Option: B

Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids. It is revealed, for example, in the floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects (e.g. water striders) to run on the water surface.

In the late of 17th century British scientist Isaac Newton studied cooling of bodies. Experiments showed that the cooling rate is approximately proportional to the difference of temperatures between the heated body and the environment. This fact can be written as the differential relation : dQ dt A T T S= abg, where A is the surface area of the body through which the heat is transferred, T is the temperature of the body, TS is the temperature of the surrounding environment, á is the heat transfer coefficient depending on the geometry of the body, state of the surface, heat transfer mode, and other factors. Surface area or volume ratio is an important influence on temperature control. For same volume sphere has minimum surface area, while circular plate has maximum surface area. So sphere cools slowest and plate cools fastest.

Correct Option: C

In the late of 17th century British scientist Isaac Newton studied cooling of bodies. Experiments showed that the cooling rate is approximately proportional to the difference of temperatures between the heated body and the environment. This fact can be written as the differential relation : dQ dt A T T S= abg, where A is the surface area of the body through which the heat is transferred, T is the temperature of the body, TS is the temperature of the surrounding environment, á is the heat transfer coefficient depending on the geometry of the body, state of the surface, heat transfer mode, and other factors. Surface area or volume ratio is an important influence on temperature control. For same volume sphere has minimum surface area, while circular plate has maximum surface area. So sphere cools slowest and plate cools fastest.

Optical fibres are used in endoscopic instruments that enable doctors to view internal body parts without having to perform surgery. Fernando Alves Martins of Portugal invented the first fiber optic endoscope in 1963-64. Further innovations included using additional fibres to channel light to the objective end from a powerful external source, thereby achieving the high level of full spectrum illumination that was needed for detailed viewing, and colour photography. The previous practice of a small filament lamp on the tip of the endoscope had left the choice of either viewing in a dim red light or increasing the light output - which carried the risk of burning the inside of the patient. Alongside the advances to the optical side, the ability to ‘steer’ the tip was developed, as well as innovations in remotely operated surgical instruments contained within the body of the endoscope itself. This was the beginning of “key-hole surgery” as we know it today.

Correct Option: D

Optical fibres are used in endoscopic instruments that enable doctors to view internal body parts without having to perform surgery. Fernando Alves Martins of Portugal invented the first fiber optic endoscope in 1963-64. Further innovations included using additional fibres to channel light to the objective end from a powerful external source, thereby achieving the high level of full spectrum illumination that was needed for detailed viewing, and colour photography. The previous practice of a small filament lamp on the tip of the endoscope had left the choice of either viewing in a dim red light or increasing the light output - which carried the risk of burning the inside of the patient. Alongside the advances to the optical side, the ability to ‘steer’ the tip was developed, as well as innovations in remotely operated surgical instruments contained within the body of the endoscope itself. This was the beginning of “key-hole surgery” as we know it today.

Since the amplitudes, frequency and the speed of both the waves are in same, hence the wavelength of the composite wave will be the same as the single wave. The distance between the adjacent nodes will be
a 2
, Speed of the wave, i.e., V = nl. Or, 20 = 10l.
So, l = 2 mm. Therefore,
a 2
= 1 mm

Correct Option: A

Since the amplitudes, frequency and the speed of both the waves are in same, hence the wavelength of the composite wave will be the same as the single wave. The distance between the adjacent nodes will be
a 2
, Speed of the wave, i.e., V = nl. Or, 20 = 10l.
So, l = 2 mm. Therefore,
a 2
= 1 mm