Exam (elaborations)
XI_Phy_New_Chap-07 Gravitation (92 A&R Items)
XI_Phy_New_Chap-07 Gravitation (92 A&R Items)
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Spread the Happiness. Assertion and Reason Statements Feedback: 9008271516XI_Phy_New_Chap-07 _ GRAVITATION
S# Correct Assertion Correct Reason
7.1 INTRODUCTION; 7.2 KEPLER’S LAWS
1 Gravity is an attractive force between objects. All material objects attract each other.
Planets move in elliptical, not circular orbits. Kepler's first law establishes the Sun lies at a focal point of
2 an elliptical planetary orbit, deviating from the Copernican
model's circles.
A planet's speed varies across its revolution. Kepler's second law explains a line connecting the Sun and
the planet sweeps equal areas in equal times. This implies
3
the planet moves faster when closer and slower when
farther from the Sun.
A planet's orbital period is related to its distance Kepler's third law establishes a mathematical relationship
4 from the Sun. between the square of a planet's orbital period and the
cube of its semi-major axis.
The law of areas follows from angular momentum This law results from angular momentum conservation,
5 conservation. applicable to central forces like gravity acting along the
Sun-planet line.
The law of areas contrasts with the Kepler's second law clarifies the misconception of
misconception of constant orbital speed. constant planetary orbital speed. The law implies the planet
6
speeds up closer to the Sun and slows down farther away.
7.3 UNIVERSAL LAW OF GRAVITATION
Newton's Law of Gravitation: Universal Attraction Every object attracts every other object.
7
Weaker moon's centripetal acceleration suggests Supports inverse-square relationship between gravitational
8
a distance-dependent force. force and distance.
Newton's Law describes force between point Formula F = (G * m * m ) / r² provided.
9 masses mathematically (Gravitational Constant
G).
Gravitational force is attractive, pulling objects Acts along the line connecting object centers.
10
together.
Total force on a point mass considers Vector sum of individual gravitational forces exerted by
11
contributions from all surrounding masses. other objects.
Law requires summation of forces for objects Not directly applicable to objects with mass distributed
12
with finite size (extended objects). throughout their volume.
Hollow spherical shell's attraction acts as if mass Perpendicular force components from different regions
14
concentrated at center. cancel out.
No net force exists inside a hollow spherical Gravitational forces from various regions cancel each other
15
shell. completely.
7.4 THE GRAVITATIONAL CONSTANT
Cavendish experiment determined the Measured torque caused by gravitational attraction
16
gravitational constant (G). between masses.
Torque due to gravitational force depends on F x L (Force multiplied by the length of the bar).
17
force and bar length.
Angle of twist (q) is proportional to restoring Achieves equilibrium when restoring torque balances the
18
torque on the wire. torque caused by gravitational force.
Gravitational constant (G) quantifies gravitational Strength of attraction between two objects is proportional
force in Newton's Law. to G, their masses, and inversely proportional to the square
19
of the distance between them.
7.5 ACCELERATION DUE TO GRAVITY OF THE EARTH
Earth's mass acts as if concentrated at its center All concentric Earth shells exert a combined gravitational
20 for external points. pull as if their mass is at the center (Shell Theorem).
Point inside Earth experiences no force from
Point lies within those shells, and their mass is negligible
21
outer shells. according to the shell theorem.
Gravitational force on an interior point depends
Only inner shells contribute; their effective mass is
22
on its distance from Earth's center. proportional to the radius cubed.
Cavendish experiment with G, g, and Earth'sG (gravitational constant), g (acceleration due to gravity),
23 radius estimates Earth's mass. and Earth's radius relate to Earth's mass through the force
equation (F = GMm/R²).
7.6 ACCELERATION DUE TO GRAVITY BELOW AND ABOVE THE SURFACE OF EARTH
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