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Potential

Devna asked.

find the potential at A ….a prson brings a mass of 1 kg from infinity to the pt A .initially the mass was at rest but it moves at a speed of 2 m/sas it reches A .the work done by person on mass is -3 J

Weight and inertia on moon

Say True or False; An object on the Moon weights 1/6 of what it weights on the Earth. Therefore, the object has less inertia on the Moon.( Justify your answer)

Answer: The statement is false.

Inertia depends on mass and not on weight. The weight on moon is less not because of a decrease in mass, but due to the decrease in the acceleration due to gravity on the surface of moon.

Inertia depends on mass and there is no change in mass when a body is taken to moon. Therefore the inertia of a body is same on moon as that on earth or anywhere else in the universe, even in a gravity free space.

Physics of Diving

When a high diver in a swimming event springs from the board and “tucks in”, a rapid spin result. Why is this?

Answer: This is the consequence of conservation of angular momentum.

The angular momentum of a body is the product of Moment of inertia (A measure of rotational inertia and it depends on the mass as well as distribution of mass about the axis of rotation. Farther the masses, greater will be the rotational inertia) and the angular velocity (The speed of rotation)

The angular momentum of a body remains unchanged in the absence of any external torque.

When the diver dives, he is giving his body a turning and takes off with his limbs stretched. In the stretched position, the moment of inertia is more. When he “tucks in”, the moment of inertia decreases. But since this happens without any external torque, it would result in an increase in angular velocity so as to keep the angular momentum constant.

Physical Quantity

Prabesh wants to know more on Physical quantities:

Physical Quantity is a quantity which can be measured. eg; length, mass, force, time etc

(The quantities which cannot be measured are abstract. Eg; Love, anger intelligence)

Momentum and Kinetic Energy

Two bodies one light and other heavy have equal momentum.Which of them has higher kinetic energy?

(Aajma Manoj asked)

Answer:

The lighter body will have greater kinetic energy.

Explanatiom

Momentum, p=mv

squaring both sides, p2 = m2v2

Kinetic Energy = 1/2 mv2 = p2/2m

Therefore, for bodies of equal momenta, kinetic energy is inversely proportional to mass.

Nature of light, relativity and blackholes

Prasanna asked:

we know light has got dual nature. & blackholes has got enormous gravity from which even light cant escape. how can gravity can influence a mass less stream of particles like gravity?

Ans:

Do you know why solar eclipse is watched with great importance by the scientific community?

OK

Einstein’s theory of General Relativity was proved right(?) when bending of light by masses was observed in reality.

Please go through the links below and hope that you’ll find an answer there.

http://en.wikipedia.org/wiki/General_relativity

http://www.suite101.com/

Recent Research Publications in Physics

Mass of Neutrino

The absolute scale of neutrino masses is very important for understanding the evolution and the structure formation of the Universe as well as for nuclear and particle physics beyond the present standard model.

Elastic Scattering of He at the surface of liquid helium

Elastic scattering of 4He atoms when they approach the surface of 4He liquid, has been studied. The liquid surface is assumed to be uniform and the density profile is the same along and perpendicular to the surface. The incident 4He atom will interact with a large number of 4He atoms in the liquid near the surface of liquid 4He. Hence, the effective interaction of the incident particle will be due to many-body forces.

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