Mechanics · Intermediate · ⏱ 30 min

Circular Motion & Centripetal Force

Lock a body into circular orbit using a radial force, measure the centripetal acceleration a = v²/r, and find out what happens when the string snaps.

Step 01

Create a Circular Orbit

Drag a Circle body to the canvas. In Force Settings, add a Central Force pointing toward the origin. Set the magnitude to keep the body in a circular path at radius r = 5 m. Hint: start with F = mv²/r and tune until the orbit is stable.

Note: If the orbit spirals inward, the force is too strong. If it spirals outward, increase the force. Use the trajectory trace (T key) to visualise the path.
Step 02

Measure Centripetal Acceleration

Enable the graph panel and plot acceleration magnitude vs time. It should be constant. Verify against the formula a = v²/r using the measured speed from the velocity graph.

Step 03

Vary the Speed

Double the initial tangential velocity. What force is now needed to maintain the same orbit radius? Verify that F ∝ v².

Note: The force required scales with the square of velocity. This is why motorway bends need banked turns — friction alone cannot provide enough centripetal force at high speed.
Step 04

Cut the String

Remove the central force mid-orbit (use a timed force event or manually stop it). Observe: the body travels in a straight line tangent to the circle — Newton's First Law in action.

Step 05

Explore Non-Uniform Circular Motion

Add gravity to the scene. The body now has varying speed around the orbit (slower at top, faster at bottom). Plot the normal force vs position angle to see how it varies.

Key formula:
a_c = v² / r, F_c = mv² / r