Gravitational force

Mnemonic: M.A.D. (Mass, Attraction, Distance)

• Force of attraction between any two objects having mass • Acts along a line joining their centers • Directly proportional to the product of the masses of the objects • Inversely proportional to the square of the distance between the objects • Universal gravitational constant (G): - Goodness **(G)**racious! - Constant of proportionality in Newton’s law of gravitation - Value: 6.674 × 10^-11 N m^2 kg^-2

Gravitational field

Mnemonic: GF-unit (Gravitational Force per unit mass)

• Gravitational force experienced by a unit mass placed at a point • Represented by the letter g • Direction: Towards the center of the object creating the gravitational field • Magnitude: Equal to the gravitational force acting on a unit mass • Gravitational field intensity (g):

• Gravity **(g)**otcha! - Ratio of the gravitational force acting on an object to its mass
• SI unit: N kg^-1 or m s^-2

Weight of an object

Mnemonic: W = m(G)eorge

• Gravitational force acting on an object due to the presence of another massive object • Depends on the mass of the object (m) and the gravitational field strength (g) • SI unit: N

Free fall

Mnemonic: F.F. (Falling Freely)

• Motion of an object under the influence of gravity alone • Acceleration due to gravity (g):

• acceleration of an object in free fall near the Earth’s surface
• Value: 9.8 m s^-2

Projectile motion

Mnemonic: PM-X-Y

• Motion of an object thrown at an angle to the horizontal • Combination of horizontal and vertical motion • Equations of motion:

• Horizontal motion: - x = u cos θ t
• Vertical motion: - y = u sin θ t - 0.5 g t^2

Escape velocity

Mnemonic: E = mc(s)squared (Escape velocity)

• Minimum velocity required by an object to escape the gravitational pull of a massive object • For the Earth: 11.2 km s^-1

Gravitational potential energy

Mnemonic: GPE = m(G-H)-5

• Energy possessed by an object due to its position in a gravitational field • Depends on the mass of the object (m), the gravitational field strength (g), and the vertical height of the object (H) • SI unit: J

Geostationary orbit

Mnemonic: GEO-stationary: Stationary Satellites above the Equator

• Circular orbit around the Earth with the same orbital period as the Earth’s rotation • Satellites in this orbit appear to be stationary with respect to the Earth’s surface • Height: Approximately 35,786 km above the Earth’s equator