Students can go through AP Inter 1st Year Physics Notes 9th Lesson Gravitation will help students in revising the entire concepts quickly.
AP Inter 1st Year Physics Notes 9th Lesson Gravitation
→ There are four basic forces in nature, they are
a) Gravitational force
b) Electromagnetic force
c) Strong nuclear force
d) Weak nuclear force
→ Newton’s Universal Law of Gravitation : Every particle of matter in the universe attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
F ∝ \(\frac{\mathrm{m}_1 \mathrm{~m}_2}{\mathrm{~d}^2}\); F = \(\frac{\mathrm{Gm}_1 \mathrm{~m}_2}{\mathrm{~d}^2}\)
→ Gravitational field : A mass particle modifies space around it in some way and through which it interacts with other mass particles.
→ Gravitational field travels with speed of light in vacuum.
→ Black hole is dense object into which other objects could fall but out of which no object or even light could ever come out.
→ A non-accelerating frame is called inertial frame of refer-enceAn accelerating frame is called non-inertial frame of reference.
→ Inertial mass (m1) of an object and its gravitational mass (mg) are equal.
→ On the basis of principle of equivalence, the gravitational and inertial masses are equal.
→ Acceleration due to gravity at a height h
gh = \(\frac{G M}{(R+h)^2}\) = g(1 – \(\frac{\mathrm{2h}}{\mathrm{R}}\))
→ The value of decreases with depth gd = g(1 – \(\frac{\mathrm{d}}{\mathrm{R}}\))
→ The variation of g with latitude of the place on earth gΦ = g – Rw2 cos2 Φ.
→ ‘g’ value vary with latitude due to non-spherical nature of the earth.
→ Due to local conditions also the value of g will vary from place to place on the surface of the earth.
→ The orbital velocity of a projected body is the velocity with which it revolves in the orbit.
v0 = \(\sqrt{\mathrm{gR}}=\sqrt{\frac{\mathrm{GM}}{\mathrm{R}}}\) = 7.92 kms-1
→ The escape velocity of a body is the minimum velocity that should be given in order that it may overcome the earth’s attraction and go into the space.
ve = \(\sqrt{2 \mathrm{gR}}=\sqrt{\frac{2 \mathrm{GM}}{\mathrm{R}}}\) = 11.2 kms-1
→ The escape velocity of a satellite from an orbit is \(\sqrt{2}\) times the orbital velocity.
→ The geostationary satellites are in specified orbits at a height of about 36,000 km above the earth.
→ Law of orbits : All planets move in ellipitcal orbits with the sun situated at one of the foci.
→ Law of areas: The line that joins any planet to the sun sweeps equal areas in equal internals of time.
→ Law of periods : The square of the time period of revolution of a planet is proportional to the cube of the semi-major axis of the ellipse tracedout by the planet
T2 ∝ R3
→ The gravitational potential energy is given by
V = \(\frac{-\mathrm{Gm}_1 \mathrm{~m}_2}{\mathrm{r}}\)
→ Time period of polar satellites is 100 minutes.
→ Polar satellites are low altitude satellites, but they go around the poles of the earth in a north- south direction.