HP TGT Physics: Gravitation Notes & Practice MCQs
HP TGT Physics — Chapter 4: Gravitation
Ø Key
Points with Explanation
Ø Gravitation
Every object in the universe attracts every other object
with a force called Gravitational Force.
Example: Earth attracts us, keeping us on the ground.
Ø Universal
Law of Gravitation
Statement: The force of attraction between two
objects is directly proportional to the product of their masses and inversely
proportional to the square of the distance between them.
Formula:
F = G (m₁m₂) / r²
Where:
- F =
Gravitational force
- G =
Universal gravitational constant (6.67 × 10⁻¹¹ Nm²/kg²)
- m₁,
m₂ = Masses
- r =
Distance between centres
Ø Importance
of Gravitation
- Holds
planets in orbit around Sun.
- Causes
tides due to Moon’s pull.
- Holds
atmosphere around Earth.
Ø Acceleration
Due to Gravity (g)
It is the acceleration produced in a body due to Earth’s
gravitational pull.
Formula: g = G M / R²
Where:
- M =
Mass of Earth
- R =
Radius of Earth
Approximate value: g ≈ 9.8 m/s²
Ø Mass
vs Weight
- Mass:
Amount of matter; constant; SI unit: kg.
- Weight:
Force with which Earth attracts an object; W = mg; changes with gravity.
Ø Free
Fall
When only gravity acts on a falling body, it is in free
fall.
- Objects
gain speed while falling due to gravity.
Ø Motion
of Planets
Planets revolve around the Sun due to gravitational force
and inertia.
Important Formulas
|
Concept |
Formula |
|
Gravitational Force |
F = G (m₁m₂) / r² |
|
Acceleration due to gravity |
g = G M / R² |
|
Weight |
W = mg |
Ø MCQs
for Gravitation
1. What keeps planets in their orbits?
A) Electric Force
B) Magnetic Force
C) Gravitational Force
D) Nuclear Force
2. What is the value of G?
A) 6.67 × 10⁻¹¹ Nm²/kg²
B) 9.8 m/s²
C) 3 × 10⁸
m/s
D) 1.6 × 10⁻¹⁹
C
3. Which of these is a scalar quantity?
A) Force
B) Weight
C) Mass
D) Acceleration
4. If Earth’s radius increases, value of g:
A) Increases
B) Decreases
C) Remains same
D) Becomes zero
5. Free fall means:
A) Object is at rest
B) No force acts
C) Only gravity acts
D) Only air resistance acts
Ø Quick
Revision Tip:
👉 Focus on Universal Law
formula, value of G, difference between mass & weight, and free fall
examples.
Ø Next
Chapter:
👉 Coming Up: Work,
Energy & Power — oh wait, already done! Next: Motion of System of Particles
& Rigid Body.
FAQs
A1. It states that every object attracts every other object with a force proportional to their masses and inversely proportional to the square of the distance between them.
Q2. What is the value of gravitational constant G?
A2. 6.67 × 10⁻¹¹ Nm²/kg².
Q3. What is the difference between mass and weight?
A3. Mass is constant and measures matter; weight is the force of gravity acting on mass.
