A satellite orbits the Earth at a constant speed in a circular path. Why does the satellite not fly off into space in a straight line, according to Newton's First Law of Motion?
- AThe satellite's engine constantly provides thrust to curve its path.
- BThe Earth's gravitational pull provides a centripetal force.
- CThere is no friction in space to slow it down.
- DIts inertia keeps it in orbit.
Show answer & explanationAnswer & explanation
Correct answer: B. The Earth's gravitational pull provides a centripetal force.
Newton's First Law states an object in motion will continue in a straight line unless acted upon by an external force. For an object to move in a circular path, a constant inward force (centripetal force) is required. In the case of a satellite, this centripetal force is provided by the Earth's gravitational pull, which continuously pulls the satellite towards the Earth, preventing it from flying off tangentially.
Why the other options are wrong
- A. Satellites typically do not use continuous thrust to maintain orbit; gravity is the primary force.
- C. While true, lack of friction explains why it doesn't slow down, not why it curves its path.
- D. Inertia would cause it to continue in a straight line, not to orbit in a curve.
Centripetal Force (Orbital Motion)
The net force required to keep an object moving in a circular path. For satellites orbiting a planet, this force is provided by the gravitational attraction between the satellite and the planet.
- Always directed towards the center of the circular path.
- Causes a change in direction (acceleration), not speed (if speed is constant).
- Without it, an object in circular motion would fly off tangentially.
Memory trick: Gravity's grip keeps the 'centripetal' curve in the 'orbital' dance.