{"product_id":"celtrix-the-rattleback-physics-t-shirt","title":"Celtrix – The Rattleback Physics T-Shirt","description":"\u003cp\u003eSpin Celtrix the wrong way and she wobbles, rattles, and spins back the other way.\u003c\/p\u003e\u003ch3\u003eThe Physics\u003c\/h3\u003e\u003cp\u003eA rattleback is a boat-shaped top whose mass axes are slightly twisted relative to its curved base (δ ≠ 0). Friction at the contact point couples wobbling to spinning, so in the unfavoured direction spin turns into rocking and then back into spin the other way. Angular momentum is not violated: the friction force at the contact exerts the torque.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003edL\/dt = r_c × F_c\u003c\/strong\u003e\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003eL: angular momentum (kg·m²\/s)\u003c\/li\u003e\n\u003cli\u003et: time (s)\u003c\/li\u003e\n\u003cli\u003er_c: position of the contact point from the centre of mass (m)\u003c\/li\u003e\n\u003cli\u003eF_c: contact force from the table (N)\u003c\/li\u003e\n\u003cli\u003eδ: misalignment angle (rad)\u003c\/li\u003e\n\u003c\/ul\u003e\u003cp\u003eG. T. Walker analysed it in 1896.\u003c\/p\u003e\u003cp\u003e\u003cem\u003eHonest caveat:\u003c\/em\u003e Some celts reverse more than once; not every rattleback reverses in only one direction.\u003c\/p\u003e\u003ch3\u003eOn the shirt\u003c\/h3\u003e\u003cp\u003eFront: Celtrix, the pixel-art character, with the title. Back: the torque equation, the misalignment angle, the friction explanation and Walker's 1896 paper. Printed on a unisex tee.\u003c\/p\u003e","brand":"Printify","offers":[{"title":"S \/ White","offer_id":50936441307239,"sku":"23796504507699589674","price":29.99,"currency_code":"USD","in_stock":true},{"title":"S \/ Black","offer_id":50936441340007,"sku":"16702883706018209189","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ White","offer_id":50936441372775,"sku":"71550508608660282453","price":29.99,"currency_code":"USD","in_stock":true},{"title":"M \/ Black","offer_id":50936441405543,"sku":"29524288225021342243","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ White","offer_id":50936441438311,"sku":"11728669484770819102","price":29.99,"currency_code":"USD","in_stock":true},{"title":"L \/ Black","offer_id":50936441471079,"sku":"20664476171096720969","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ White","offer_id":50936441503847,"sku":"25655946295122765397","price":29.99,"currency_code":"USD","in_stock":true},{"title":"XL \/ Black","offer_id":50936441536615,"sku":"15187652532453987124","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ White","offer_id":50936441569383,"sku":"29824680608311999307","price":29.99,"currency_code":"USD","in_stock":true},{"title":"2XL \/ Black","offer_id":50936441602151,"sku":"25682074591300178539","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ White","offer_id":50936441634919,"sku":"56487426646071066892","price":29.99,"currency_code":"USD","in_stock":true},{"title":"3XL \/ Black","offer_id":50936441667687,"sku":"25329735574695604533","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ White","offer_id":50936441700455,"sku":"28639990603977092679","price":29.99,"currency_code":"USD","in_stock":true},{"title":"4XL \/ Black","offer_id":50936441733223,"sku":"20251188424276873159","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ White","offer_id":50936441765991,"sku":"13893538756324856470","price":29.99,"currency_code":"USD","in_stock":true},{"title":"5XL \/ Black","offer_id":50936441798759,"sku":"24401275607104227594","price":29.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0596\/8746\/9159\/files\/rattleback_front_16_white.png?v=1793595212","url":"https:\/\/pixelatedphysics.com\/it\/products\/celtrix-the-rattleback-physics-t-shirt","provider":"Pixelated Physics","version":"1.0","type":"link"}