Class 11 · Laws of Motion

Centripetal Force (String)

Mass on a string in circular motion — tension provides T = mv²/r live.

Key Notes

01

Mass on string in horizontal circle: tension T provides the centripetal force.

02

T = mv²/r = mω²r — increases with v² (or ω²) and decreases with r.

03

Cut the string and the mass flies off tangentially (Newton's 1st law).

Formulas

Centripetal force

Always toward center.

Period

Time for one revolution.

Important Points

Centripetal force is NOT a new force — it's whatever real force points to center (tension, gravity, normal, friction).

Direction: toward the center; speed magnitude is constant in uniform circular motion.

Centripetal Force (String) notes from sciphylab (also known as SciPhy, SciPhy Lab, SciPhy Labs, Physics Lab). Class 11 physics revision for JEE Mains, JEE Advanced, NEET UG, AP Physics 1/2/C, SAT, and CUET-UG.