Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Kepler's Second Law using a centripetal force kit

Class practical

The simple kit demonstrates the increase in speed with a diminishing radius of orbit.

Apparatus and materials

For each student or group of students

Centripetal force kit

Health & Safety and Technical notes

Ensure that the bungs are securely attached and that each student has sufficient space to whirl the bung safely.

The centripetal forces kit is available from: Technology Supplies Limited.

centripetal force kit



a Set the bung whirling around the top of the apparatus.
b Pull on the thread to increase the load.


Teaching notes

1 Kepler's Second Law states that a planet in its orbit sweeps out equal areas in equal times. The time of orbit of the puck will fall as its radius of orbit decreases.
2 You can measure the load by attaching a newton meter to the bottom of the string. As the force on the puck is increased, its orbit gets smaller and its speed increases.



Technology Supplies Limited