Hi guys, I am new to this forum, but I am in desperate need of help on something for my Final year university project. I have designed a Trolley and need to calculate some forces. Does anyone know the formula to calculate the pushing forces required to stop this trolley from moving. Weight of trolley is 1687 Newtons the force of the spring pushing the rubber pad 98.1N. The trolley is traveling around walking pace, 4mph. Force required to move trolley forward is about 27N on level ground (road) So currently 98.1N are pushing on the Pneumatic wheel, but I am not sure whether or not this force is strong enough to prevent trolley stopping when in motion. It is a standard pneumatic wheel, with 50mm wide rubber material. The width of the rubber pad is 50mm x 50mm. Is is possible to calculate the force of friction required to stop the wheel from spinning. The pneumatic wheel has textured rubber, as does the pad, which probably increases friction. The pads act on two wheels. [PLAIN]http://img714.imageshack.us/img714/1829/trolley1.jpg [Broken] [PLAIN]http://img38.imageshack.us/img38/2768/trolleyv.jpg [Broken] Thanks!