# English Version HSC 1st Paper 7th Chapter Physics Note

English Version HSC 1st Paper 7th Chapter Physics Note. Structural Properties of Matter. The physics is one of the oldest academic disciplines, perhaps the oldest through the inclusion of astronomy. In the last two millennia, physics was a part of natural philosophy, chemistry, certain branches of mathematics and biology, but during the scientific revolution in the 17th century, the natural sciences emerged as unique in its own right research programs. Physics intersects with many interdisciplinary areas of research, such as Biophysics and quantum chemistry, and physics limits are not rigidly defined. New ideas in physics often explain the fundamentals of other sciences mechanisms, to open new avenues of research in areas such as mathematics and philosophy.

## English Version HSC 1st Paper 7th Chapter Physics Note

Structural Properties of Matter

Question No 1.

Each of two masses having 0.05kg is attached at the free ends of each of two wires with the same length of 1m and of the same element suspended from firm support. The diameters of the wires are respectively 2mm and 4mm (Young’s modulus = 2 x 1011 Nm2)

a. What is called viscosity? 1

b. Why is the drop of rain spherical? 2

c. Determine the potential energy per unit volume of the first wire. 3

d. Which one will move slowly if each of the suspended wires with the attached mass behaves as a simple pendulum? Explain with mathematical analysis. 4

The answer to the question no. 1

a. The property of the fluid which causes resistivity against relative motion between fluid layers is known as viscosity.

b. There is potential energy stored on a liquid surface which depends on the surface. This potential energy decreases with the decrease of surface area. In nature, everything becomes stable when its potential energy is the lowest. So, for the lowest potential energy, in this case, the surface area has to be minimum. For a certain volume, an object has a minimum surface area when it’s spherical in shape. That’s why raindrops shape is spherical.

c. Stored potential energy per unit volume,

E = 1/2 x stress x strain

= 0.0608 J (Ans.)

d. The first pendulum is an angular displacement of theta, the force on the wire, F = mg cos theta .: If the expansion of wire is lı, then,

So, the first pendulum runs slower than the second one.

Question No. 2.

To determine the viscous drag of water and purity of water, Tajin performed an experiment in the laboratory according to the figure.

a. What is the coefficient of viscosity? 1

b. Why does not the Poisson’s Ratio depend on the stress applied, within the elastic limit? 2

c. Determine the viscous drag of water on the iron sphere. The coefficient of viscosity of water is 3 x 10-3 Nsm-2. 3

d. In the water used in the laboratory pure? Give your decision by analyzing the result from the experiment. [The surface tension of pure water is 72 x 10-3Nm-1] 4

The answer to the question no. 2

a. Co-efficient of viscosity is defined as the tangential force per unit area required to maintain unit velocity gradient between layers of liquid.

b Poisson’s ratio is the ratio of relative lateral strain normal to the applied force to the relative axial strain in the direction of applied force. The applied must be within the elastic limit. So, Poisson’s ration depends on whether the volume of material increases or decreases or remains same when the force applied to it. This, on the other hand, depends on the property of the material. That’s why Poisson’s ratio depends on material only, hot on applied force.

Physics is one of the oldest academic disciplines and, through its inclusion of astronomy, perhaps the oldest. Over the last two millennia, physics, chemistry, biology, and certain branches of mathematics were a part of natural philosophy, but during the scientific revolution in the 17th century, these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy.

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