In the 1840s, James Prescott Joule showed that mechanical energy and heat were different forms of the same thing. To do this, Joule tied a string from a falling weight to a paddle submerged in water. As the weight fell, it pulled the string which turned the paddle which stirred the water. During this process, the temperature of the water rose. By making careful measurements, Joule was able to show that the mechanical energy lost by the falling weight was gained by the water as heat.
|The illustration of Joule's experiment features a paddle submerged in a water tank on the left and a falling weight on the right. A meter stick measures the distance the weight falls, which can be used to find the mechanical energy lost.|
My smoothie might have 250 grams of ice in the form of frozen strawberries and other fruits. The heat given off by the blender will melt some of this ice. The heat required to melt a solid is called the heat of fusion. The heat of fusion for ice is 334 Joules per gram. Since two minutes of blending only provides 120 Joules of heat, I will only melt about one-third of a gram of the ice in the container. That's about one one-thousandth of the total ice. It's much more likely the warmer air in the room is melting my smoothie. If I need the air to melt some of the smoothie before blending, I'd be better off just waiting two minutes rather than wasting energy by needlessly running the blender.
 I am, of course, referring, to Michael Myers the character who brutally murders his victims in the slasher classic Halloween, not Michael Myers the actor, who brutally murders comedy in The Love Guru.
 Within an order of magnitude, this rotational speed is typical of what you find in immersion blender advertisements.
Aaron Santos is a physicist and author of the books How Many Licks? Or How to Estimate Damn Near Anything and Ballparking: Practical Math for Impractical Sports Questions. Follow him on Twitter at @aarontsantos.