Mistake Master
Mistake Master · AP Physics C · Unit 2 · Topic 2.10 · Step-Through Animation
Centripetal Is a Job, Not a Force
You'll learnthat circular motion at constant speed still accelerates inward, and which real force supplies it.
A 0.5 kg ball whirls on a string at a steady 4 m/s and the speed never changes — yet it accelerates every instant, straight at the center. Watch the velocity turn, meet the real force holding the circle, then snap the string and see where the ball actually goes.
Before you start
What you're looking at
A ball on a string whirling in a horizontal circle, seen from above — 0.5 kg, radius 2 m, steady 4 m/s.
The question
Is the ball accelerating, which real force turns it, and where does it go if the string snaps?
Watch for
Two nearby velocity arrows subtracted to build the inward acceleration — the ball does not fly outward.
What the symbols mean
Blue arrow = velocity (4 m/s, tangent); the string is the real force doing the centripetal job; r = 2 m, m = 0.5 kg.
TOP-DOWN VIEW
Step 1 / 8