What is a gravitational field?
The region around a mass where its gravitational force can be felt.
State the Law of Universal Gravitation.
\( F = G \frac{M_1 M_2}{r^2} \)
What does \( G \) represent in gravitational equations?
The gravitational constant, \( 6.67 \times 10^{-11} \, \text{Nm}^2\text{kg}^{-2} \).
Define gravitational potential.
The work done in bringing a unit mass from infinity
to a point in the field:
\( V_g = - G
\frac{M}{r} \)
What is escape velocity?
The minimum velocity needed to escape Earth’s
gravity:
\( V_e = \sqrt{2gR} \)
State the formula for acceleration due to gravity.
\( g = \frac{F}{m} = \frac{GM}{R^2} \)
What is the SI unit of gravitational potential?
Joules per kilogram (J/kg)
State Kepler's First Law.
Planets move in elliptical orbits with the Sun at one focus.
State Kepler's Second Law.
A line joining a planet and the Sun sweeps equal areas in equal times.
State Kepler's Third Law.
\( T^2 \propto r^3 \): The square of a planet’s period is proportional to the cube of its orbital radius.
What is a satellite?
An object that orbits a planet or celestial body.
Differentiate between natural and artificial satellites.
Natural satellites occur naturally (e.g. Moon); artificial satellites are man-made and launched into orbit.
Give one example each of natural and artificial satellites.
Natural: The Moon
Artificial: Niger-SAT I
List three uses of satellites.
Weather monitoring, telecommunications, military surveillance
What is the formula for orbital velocity?
\( v = \sqrt{\frac{GM}{r}} \)
What is the significance of orbital velocity?
It allows a satellite to stay in stable circular orbit without falling back to Earth.
Name two Nigerian satellites and their launch years.
Niger-SAT I (2003), NICOM SAT I (year unspecified)
What is the purpose of NICOM SAT I?
Improved mobile and internet services across Central Africa.
List any three components of a rocket.
Propellant tank, nozzle, combustion chamber.
State Newton’s Third Law and relate it to rockets.
Every action has an equal and opposite reaction. Expelled gas pushes the rocket forward.
Give three uses of rockets.
Launching satellites, rescue operations, fireworks.
What is the function of satellite solar panels?
To power the satellite using energy from the Sun.
What causes satellites to remain in orbit?
Their tangential velocity balances gravitational pull, creating circular motion.
What is a geostationary satellite?
A satellite that orbits Earth once every 24 hours and stays fixed over one point on the equator.
What is meant by satellite payload?
The functional part of the satellite (e.g., sensors, cameras, transmitters).
Why must satellites be placed above the atmosphere?
To reduce air resistance and prevent heating from friction.
What does Kepler’s third law tell us about distant planets?
Distant planets have longer orbital periods.
How do satellites contribute to meteorology?
They collect and transmit data for weather forecasting and climate studies.
What is the relation between gravitational force and distance?
Gravitational force is inversely proportional to the square of the distance between masses.
Write the formula for gravitational potential energy.
\( U = - \frac{GMm}{r} \)
1 / 30