Flat spring for trolley

For experiments on the principle of momentum and dynamic mass determination;
Curved steel flat spring, the ends of which are specially shaped to rest on two measuring trolleys
Width of the steel flat spring: 18 mm
Dimensions: approx. 80 x 70 x 18 mm
Mass: approx. 13 g

additionally recommended:
2 x P1311-2A Trolley, mass of 50g, very low friction