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Other Sources of Centripetal Force
Tension, gravity and the normal force can each act as the centripetal force in suitable situations.
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Recommended for Class 11
Other Sources of Centripetal Force
26. Tension as Centripetal Force
For an object attached to a string and moving in a horizontal circle, tension may provide the inward force.
T = mv² / r
The tension acts along the string toward the centre.
If other radial forces are present, the net inward force—not necessarily tension alone—equals mv²/r.
27. Gravity as Centripetal Force
Gravity supplies the centripetal force for ideal circular orbits.
For a satellite:
Fg = Fc GM mr² = mv² / r
Cancelling m:
GM / r = v²
Therefore:
v = √(GM / r)
Gravity continuously changes the direction of the satellite’s velocity.
28. Normal Force as Centripetal Force
A normal contact force may provide all or part of the inward force.
Examples include:
- A vehicle on a banked road
- An object moving around the inside of a circular track
- A rotating object constrained by a surface
The correct equation is always:
Σ Finward = mv² / r
Exam Focus
Exam Focus
Important points
- Tension in a string can supply F_c
- Gravity can supply F_c in orbital motion
- Normal force can supply F_c on a surface
Common Mistakes
Common Mistakes
- Mistake
Saying acceleration is zero because speed is constant.
- Mistake
Directing centripetal acceleration outward.
- Mistake
Directing velocity toward the centre.
- Mistake
Treating centripetal force as an additional force.
- Mistake
Using diameter instead of radius.
- Mistake
Forgetting the square of velocity.
- Mistake
Assuming friction always acts opposite to the vehicle’s forward motion.
- Mistake
Using N = mg on every banked surface.
- Mistake
Ignoring other radial forces.
- Mistake
Confusing centripetal and tangential acceleration.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Tension in a string can supply F_c
Gravity can supply F_c in orbital motion
Normal force can supply F_c on a surface
Tension, gravity and the normal force can each act as the centripetal force in suitable situations.
Tension in a string can supply Fc
- Definition
- Tension, gravity and the normal force can each act as the centripetal force in suitable situations.
- Formula
- Tension in a string can supply F_c
- Critical warning
- Saying acceleration is zero because speed is constant.
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