# English Version HSC 1st Paper 5th Chapter Physics Note

English Version HSC 1st Paper 5th Chapter Physics Note. Work, energy, and power. 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 5th Chapter Physics Note

Work, Energy, and Power

Question No.1

There is a baby in a family dwelling in an apartment of the top floor of a 10 storied building of height 5 m of each floor. A tennis ball of mass 100g released by the baby through the grill of the balcony hits the ground after few moments.

a. What is the radius of gyration?  1

b. Explain the causes of creasing elastic fatigue of a body. 2

c. After how many time will the tennis ball as mentioned in the stem hit the ground? 3

d. Determining the total energy of the ball at 7th and 4th floors of the building by using the data in the stem will obey the conservation of energy – give your opinion verifying the truth of this statement.  4

The answer to the question no. 1

If a point of a rigid body is considered where total mass of the body is concentrated and moment of inertia at that point with respect to an axis of rotation is equal to take the moment of inertia of the whole body, then the distance of that point from the axis is called radius of gyration.

b. Within the elastic limit, if an object is continuously or regularly strained means the stress is increased and decreased continuously then strain will not occur with stress-strain occurs slowly and elasticity of the object reduces. In this condition, the object might snap or break below the breaking weight. This is the cause of elastic fatigue.

c. Height, h = 9 x 5m= 45 m

Mass of the ball, m= 100 g = 0.1 kg

Initial velocity, u = 0 ms-1

Acceleration due to gravity, g = 9.8 ms-2

time, t =?

We know that,

h = ut +0.5gt2

or. h=0xt+0.5xgt2

.:t=3.03 s

d. Each floor is 5m high. The height (h) of the 9th floor from the ground is 9 x 5m= 45 m. The ball is initial rest at 9th floor. So here total energy (E) = Gravitational energy, Potential energy = mgh = 0.1 x 9.8 x 45 = 44.1 Joule. When the ball reaches level 7th floor, it has now both kinetic (Ex) and gravitational potential (E) energy. The height (h) of the 7th floor from the ground = 35m. And distance (x) between the 9h floor and 7th floor is 10m.

Total energy (E) = Ek + Ep = my+ mgh

.: = 44.1 Joule

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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