Physics Questions

Processes that require or give off heat will be limited to changes of state, known as phase changes, and changes in chemical constitution, or chemical reactions. Changes of state involve a solid melting, a liquid freezing, a liquid boiling or a gas condensing.

An exothermic process is one that gives off heat, which is transferred to the surroundings. An endothermic process is a reaction which heat has to be supplied to the system from the surroundings.

Here in all the given options, heat is taken away from them to change there phase. 

Liquid to Solid --- Freezing

Gas to Liquid --- Condensation

Gas to Solid --- Deposition 

are all examples of exothermic processes.

Solar radiation instruments may be produced to measure different types of solar energy. When sunlight encounters the Earth's atmosphere, some of it is absorbed or scattered by water vapor, aerosols, clouds, and other air molecules. The radiation which penetrates to the Earth's surface is termed direct solar radiation.

A thermopile pyranometer is a type of actinometer used for measuring solar radiation on a planar surface and it is designed to measure the solar radiation flux density (W/m2) from the hemisphere above within a wavelength range 0.3 μm to 3 μm.

It is to overcome this opposite frictional force , that  we have to apply the needed force to make the body move

Megahertz is used to measure wave frequencies, as well as the speed of microprocessors. One MHz represents one million cycles per second. The speed of microprocessors, called the clock speed.

A photon’s relativistic momentum is given by the equation,E = pc where p is the momentum.

P = 10 MeV/c

So, E = 10 MeV

Phototropism is the ability of a photosynthesizing organism, to grow directionally in response to a light source. It is very common in plants, but can also occur in other organisms such as fungi.

Example :: Sunflower

without this centripetal force, circular motion is not possible. It acts radially towards the centre and if this force is removed there will be no circular motion but the revolving body will fly off at a tangent.

Before transferring the fish, the position is the man with the fish and the bucket of water. After transferring the position is: the man without the fish, but the fish inside the water in the bucket. Thus to know  whether there is any change in weight, it is enough to consider whether there is any change in weight when the fish in air is transferred into the water. The answer is there is no change as when in water though it loses weight due to upthrust of water on it, the level of water increases and exerts an equal force at the bottom.So, (c) is correct.