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{"activity_order":null,"activity_type":["Science"],"assignment_recipes":null,"author_notes":null,"cooked_this":0,"created_at":"2013-03-12T02:44:02Z","creator":null,"currently_editing_user":null,"description":"Most of us use a blender without giving thought to how they do the job of cutting food down to size. You might assume that the fast spinning blades cut the food directly. But blenders have a secret. Cutting is only important for the first stage of blending. Once the bits of become small and begin to flow, unseen forces come into play. After you watch this video, be sure to see [part 2](http://www.chefsteps.com/activities/the-physics-of-blending-cavitation) for the physics of cavitation.","difficulty":"","featured_image_id":"{\"url\": \"https://www.filepicker.io/api/file/jYNlxxzZQS1n1iFFJvkA\", \"size\": 246575, \"type\": \"image/jpeg\", \"key\": \"gjJ5hbk2Qm67bTyg9sIP_Physics%20of%20Blending_impact_1.jpg\", \"filename\": \"Physics%20of%20Blending_impact_1.jpg\"}","forks":[],"id":213,"image_id":"","include_in_gallery":true,"last_edited_by_id":null,"layout_name":null,"likes_count":3,"published":true,"published_at":"2013-03-12T02:44:02Z","show_only_in_course":false,"slug":"the-physics-of-blending-cutting-food-down-to-size","source_activity_id":null,"source_type":0,"summary_tweet":null,"timing":"","title":"The Physics of Blending \u2014 Cutting Food Down to Size","transcript":"Most of us use a blender without giving thought to how they do the job of cutting food down to size. Like most people, you might assume that the fast spinning blades cut the food directly. But blenders have a secret. Cutting is only important for the first stage of blending, once the bits of become small and begin to flow, unseen forces come into play.\r\n\r\nTruly powerful blenders, like this Waring Xtreme, generate hydrodynamic forces that impart the energy needed to turn even the toughest foods silky smooth. \r\n\r\nAs the blade sweeps through the fluid at the bottom of a blender, intense shearing forces literally rip particles of food apart. But it's the seemingly benign implosion of bubbles that is truly violent. These forces are normally all but invisible, but using our high-speed camera we can slow time and let you see how blending really works.\r\n\r\nInitially, the impact of the blades cut the food directly. This is important because for a blender to work, pieces of food must be small enough to start to flow under stirring action of the blades. \"Does it flow?\" is the answer to the question \"will it blend?\"\r\n\r\nA commercial-grade blender, like our Waring, has enough power that the impact of its blades can shatter some tough stuff such as handfuls of whole spices like cinnamon stick, cloves, star anise, and peppercorns into a fine powder. Even a fistful of golf balls can quickly be cut into bits...\r\n\r\nBut at some point, the pieces don't become any smaller for two reasons: As they shrink in size, the chance that the blade will hit them decreases\u2014they've simply become too small a target. The second reason is more fundamental; as the pieces become smaller, it takes vastly more kinetic energy to break them smaller still. At some point, the blade simply cannot hit the food hard enough.\r\n\r\nIn the next video, we'll explore the hidden forces that do the real work of blending food smooth.\r\n","updated_at":"2013-06-07T11:02:38Z","used_in":[],"yield":"","youtube_id":"eCJ313gICFg","tags":[{"id":2,"name":"science"},{"id":5,"name":"physics"},{"id":122,"name":"Blending"},{"id":123,"name":"cutting"}],"equipment":[],"ingredients":[],"steps":[{"activity_id":213,"audio_clip":"","audio_title":"","created_at":"2013-03-12T02:44:02Z","directions":"For solid foods, the first stage of blending is to cut, chop, or smash the food into progressively finer particles. Because most foods have either high water or oil content, the blender quickly fills with a flowing liquid.","hide_number":null,"id":756,"image_description":"","image_id":"{\"url\": \"https://www.filepicker.io/api/file/Fj1Pr2FWSD2My94zwALw\", \"size\": 177889, \"type\": \"image/jpeg\", \"key\": \"19g0dTaqSj6vDvXpd9R1_Physics%20of%20Blending_impact_3.jpg\", \"filename\": \"Physics%20of%20Blending_impact_3.jpg\"}","is_aside":null,"step_order":8388605,"subrecipe_title":null,"title":"Cutting down to size","transcript":null,"updated_at":"2013-03-27T20:19:47Z","youtube_id":"","ingredients":[]},{"activity_id":213,"audio_clip":"","audio_title":"","created_at":"2013-03-12T02:44:02Z","directions":"Reducing the size of the particles is important because, for a blender to work, pieces of food must be small enough to start to flow under stirring action of the blades. \"Does it flow?\" is the answer to the question \"Will it blend?\"","hide_number":null,"id":757,"image_description":"","image_id":"{\"url\": \"https://www.filepicker.io/api/file/kDm9C9fJRMe4W36nmD54\", \"size\": 490668, \"type\": \"image/jpeg\", \"key\": \"oopFP3CES46dcyLPl2ch_Physics%20of%20Blending_impact_2.jpg\", \"filename\": \"Physics%20of%20Blending_impact_2.jpg\"}","is_aside":null,"step_order":8388606,"subrecipe_title":null,"title":"Does it flow?","transcript":null,"updated_at":"2013-03-27T20:19:49Z","youtube_id":"","ingredients":[]},{"activity_id":213,"audio_clip":"","audio_title":"","created_at":"2013-03-12T02:44:02Z","directions":"At some point, the pieces can't be cut any smaller for two reasons: As they shrink in size, the chance that the blade will hit them decreases\u2014they've simply become too small a target. \r\n\r\nThe second reason is more fundamental; it takes a lot of energy to cut food into tiny pieces. As the pieces become smaller, it takes vastly more kinetic energy to break them smaller still. At some point, the blade simply cannot hit the food hard enough. \r\n\r\nAt this point, a lot of the energy from the fast-spinning blades actually causes the temperature of what's in the blender to rise through friction. But, as we explain [here](http://www.chefsteps.com/activities/the-physics-of-blending-cavitation), part of the energy goes into powerful hydrodynamic forces that also help to make the puree smoother still.","hide_number":null,"id":758,"image_description":"","image_id":"{\"url\": \"https://www.filepicker.io/api/file/vipgtX0URZiaPlAjB2a9\", \"size\": 246575, \"type\": \"image/jpeg\", \"key\": \"nHQDDwWQTCyTSmEzMrrv_Physics%20of%20Blending_impact_1.jpg\", \"filename\": \"Physics%20of%20Blending_impact_1.jpg\"}","is_aside":null,"step_order":8388607,"subrecipe_title":null,"title":"The limits to cutting smaller","transcript":null,"updated_at":"2013-03-27T20:19:50Z","youtube_id":"","ingredients":[]}]}