Science 1 - Chapter 1: Gravitation
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21 Terms
Define centripetal force
The force acting on any object moving along a circle, directed towards the centre of the circle.
State Kepler's First Law
The orbit of a planet is an ellipse with the Sun at one of the foci.
State Kepler's Second Law
The line joining the planet and the Sun sweeps equal areas in equal intervals of time.
State Kepler's Third Law and give its mathematical formula
The square of its period of revolution around the Sun is directly proportional to the cube of the mean distance of a planet from the Sun.
T² ∝ r³
T² / r³ = constant = k
What is an ellipse? State its focal property.
An ellipse is the shape obtained when a cone is cut by an inclined plane.
Property: The sum of the distances of the two focal points from any point on the curve is constant.
What is the value and SI unit of G?
6.673 × 10^-11 N m² / kg²
SI unit: N m² / kg²
Where is the radius of the Earth the highest (maximum) and smallest (minimum)?
Highest (Maximum): At the Equator.
Smallest (Minimum): At the Poles.
Where is the value of g highest and smallest on Earth, and what are those values?
Highest (Maximum): 9.832 m/s² at the Poles
Smallest (Minimum): 9.78 m/s² at the Equator
What is the average radius (R) and mass (M) of the Earth?
Radius (R): 6.4 × 10^6 m or 6400 km
Mass (M): 6 × 10^24 kg
Why does g decrease as you go deep inside the Earth?
Going inside decreases your distance to the center, but the effective mass of the Earth pulling you also decreases.
The drop in mass overcomes the distance change, so g decreases
What is Mass? State its type, SI unit, and whether it changes with location.
Definition: The amount of matter present in an object.
Type: Scalar quantity.
SI Unit: Kilogram (kg)
Constancy: it Remains the SAME everywhere.
What is Weight? State its formula, type, SI unit, and whether it changes with location.
Definition: The force with which the Earth attracts an object
Type: Vector quantity.
SI Unit: Newton (N)
Constancy: CHANGES from place to place.
What are gravitational waves?
Invisible ripples in the fabric of spacetime
Free Fall
Whenever an object moves only under the influence of the force of gravity alone, it is said to be falling freely.
Why is a true free fall only possible in a vacuum?
During free fall in air, air friction and buoyant force oppose the object's motion; removing air in a vacuum eliminates these forces, leaving only gravity.
Why are the moon and artificial satellites considered to be in free fall?
Because they are moving only under the influence of the gravitational field of the earth with no other forces acting on them.
What is escape velocity?
The minimum initial velocity required for an object to overcome a planet's gravitational pull and escape forever without falling back.
Potential Energy (Definition)
The energy stored in an object because of its position or state.
Potential Energy (Behavior with Height)
Potential energy is relative and increases as an object reaches greater heights from the surface of the earth.
Value of g in a Space Station
In the space station, the value of g is 11% less than its value on the surface of the earth.
Cause of Weightlessness in Space
Weightlessness is caused by space travellers and objects being in a state of free fall due to their velocity along the orbit.
