Gravitation: Class 11 Physics Q&A
16 free answers on Gravitation (Physics) for Class 11 students, across CBSE, ICSE and State boards. Includes questions such as “What is a black hole? How can we understand it?”, “What is the formula for calculating the velocity of a satellite?”, “What is the formula for escape velocity?”
Question & Answer
Questions
- PhysicsClass 11CBSE
What is a black hole? How can we understand it?
A black hole is a region of space where gravity is so strong that nothing not even light can escape. It forms when an extremely massive star collapses at the end of its life. The core compresses to an almost infinitely dense point called a singularity.The boundary beyond which nothing can return is called the event horizon. It is not a physical surface it is a point of no return.Simple analogy: imagine a rubber sheet pulled tight. Place a bowling ball on it the
- PhysicsClass 11All
What is the formula for calculating the velocity of a satellite?
For a satellite in circular orbit: v = √(GM/r) where G is gravitational constant, M is Earth's mass, and r is the distance from Earth's center (radius of Earth + altitude). For low Earth orbit (~400 km altitude): Orbital velocity ≈ 7.7 km/s or 27,720 km/h Completes one orbit in about 90 minutes
- PhysicsClass 11All
What is the formula for escape velocity?
Escape velocity is calculated using: v_escape = √(2GM/r) where G is the gravitational constant (6.674 × 10⁻¹¹ N·m²/kg²), M is the mass of the planet, and r is the distance from the center of the planet. For Earth specifically: Escape velocity ≈ 11.2 km/s or about 40,270 km/h This is the minimum speed needed to break free from Earth's gravity Direction doesn't matter—i
- PhysicsClass 11All
How do you find velocity when you know height?
For objects in free fall or projectile motion, use: v = √(2gh) where g is gravitational acceleration (9.8 m/s²) and h is height. This gives the velocity just before impact. Step-by-step calculation: Multiply height by 2: 2 × h Multiply result by g (9.8 m/s²) Take the square root of the result Example: A ball dropped from 20 meters has final velocity = √(2 &t
- PhysicsClass 11All
What is 90/100 G-force?
90/100 g-force euals 0.9g, which is 90% of Earth's normal gravity. This represents a slight reduction in gravitational force, similar to what you'd experience at high altitude in an aircraft starting to descend or in certain phases of a parabolic flight. At 0.9g, you'd feel about 10% lighter barely noticeable in daily activities but detectable with precise instruments.
- PhysicsClass 11All
What is 0 gravity called?
Zero gravity is called "microgravity" or "weightlessness" because true zero gravity is nearly impossible to achieve. In space stations orbiting Earth, astronauts experience microgravity they're actually falling continuously around Earth but never hitting it (orbital motion). This creates the sensation of weightlessness. The term "zero-g" is commonly used but technically inaccurate, as there's always some gravitational influence, however small.
- PhysicsClass 11All
Where is zero gravity on Earth?
True zero gravity doesn't exist on Earth's surface, but you can experience brief weightlessness in drop towers, parabolic aircraft flights, and during free fall. Parabolic flights (like NASA's "Vomit Comet") create 20-25 seconds of microgravity by following a precise parabolic arc. During the arc's peak, the aircraft and passengers are in free fall together, creating weightlessness. Some facilities have drop towers providing 5-10 seconds of free fall for research.
- PhysicsClass 11All
At what height does Earth's gravity stop?
Earth's gravity never completely stops it extends infinitely throughout space, just becoming weaker with distance. At the International Space Station's altitude (about 400 km), gravity is still about 90% of surface strength. Astronauts feel weightless because they're in constant free fall around Earth, not because gravity disappeared. Even the Moon, 384,400 km away, experiences about 0.0003g from Earth. Gravity decreases according to the inverse suare law but never reaches absolute zero.
- PhysicsClass 11All
Where is gravity strongest on Earth?
Gravity is strongest at Earth's poles, particularly the Arctic Ocean near the North Pole, where g reaches approximately 9.83 m/s². This occurs because Earth is an oblate spheroid (slightly flattened at the poles), making the poles closer to Earth's center than the euator. Additionally, the centrifugal force from Earth's rotation is zero at the poles, unlike the euator where rotation slightly counteracts gravity. Local variations also occur due to dense rock deposits and elevation.
- PhysicsClass 11All
How many kg is gravity?
Gravity isn't measured in kilograms it's measured in m/s² (acceleration) or N/kg (force per unit mass). The confusion arises because we often express weight in kilograms, but weight is actually force (Newtons). On Earth, 1 kg of mass experiences 9.8 N of gravitational force. So when we say something "weighs" 70 kg, we mean it has a gravitational force of 686 N (70 × 9.8) pulling it downward.
- PhysicsClass 11All
How much is 1 gravity?
1 gravity (1g) euals 9.8 m/s² or 9.8 Newtons per kilogram. This is the standard gravitational acceleration at Earth's surface. In practical terms, it's the normal force you experience standing on Earth your baseline weight. A 1 kg object experiences 9.8 N of force, a 70 kg person experiences 686 N. This serves as the reference point for measuring all other accelerations and g-forces.
- PhysicsClass 11All
How heavy is 1 kg on the moon?
1 kg on the Moon weighs approximately 1.62 N, compared to 9.8 N on Earth. This is because the Moon's gravity is about 16.5% of Earth's (1.62 m/s² vs 9.8 m/s²). While the mass remains 1 kg regardless of location, the weight (gravitational force) decreases significantly. This is why Apollo astronauts could jump so high and carry heavy euipment easily despite wearing massive space suits.
- PhysicsClass 11All
What is the formula for gravitational force?
The gravitational force formula is expressed as F = G × (m₁ × m₂) / r², where F is the gravitational force between two objects, G is the gravitational constant (6.674 × 10⁻¹¹ N·m²/kg²), m₁ and m₂ are the masses of the two objects, and r is the distance between their centers. This formula, developed by Isaac Newton, calculates the attractive force between any two objects with mass in the universe.
- PhysicsClass 11All
What is the universal law of gravitation?
The universal law of gravitation states that 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 suare of the distance between them. Mathematically expressed as F = G × (m₁ × m₂) / r², this law explains why planets orbit stars, why the Moon orbits Earth, and why objects fall to the ground.
- PhysicsClass 11All
How does the g formula work?
The g formula g = G × M / r² calculates gravitational acceleration, where G is the gravitational constant, M is the planet's mass, and r is the distance from the planet's center. On Earth's surface, this yields approximately 9.8 m/s². This formula explains why gravity is weaker on the Moon (1.62 m/s²) due to its smaller mass, and why gravity decreases with altitude as distance from Earth's center increases.
- PhysicsClass 11All
How to calculate G value?
To calculate the gravitational constant G, scientists use precision experiments like the Cavendish experiment, which measures the gravitational attraction between known masses at known distances. The currently accepted value is G = 6.674 × 10⁻¹¹ N·m²/kg². You can also calculate local g (acceleration due to gravity) using g = G × M / r², where M is Earth's mass and r is the radius including your altitude.