These are fundamental to all physics curricula. One of the three wheel carts has an exploder mechanism with two levels of spring tension, the other does not. Suitable for investigating Newton's Laws, conservation of momentum, and explosions. Low friction ball bearings are strong enough to carry additional masses on the 9 cm x 30.5 cm plastic covered top. A trigger on the top releases the exploder without applying a horizontal force. Includes 10 towing bands for applying a constant force during motion studies.