Which of these is an experiment generally regarded as being first carried out by james joule?
observing that objects increase in temperature when heated with fire
showing that friction slows down the motion of objects
measuring the temperature increase of water from doing work stirring it
testing the mechanical advantage of pulleys

Agymnast dismounts off the uneven bars in a tuck position with a radius of 0.3m (assume she is a solid sphere) and an angular velocity of 2rev/s. during the dismount she stretches out into the straight position, with a length of 1.5m, (assume she is a uniform rod through the center) for her landing. the gymnast has a mass of 50kg. what is her angular velocity in the straight position?

The desk has a weight of 75 lb and a center of gravity at g. determine the initial acceleration of a desk when the man applies enough force f to overcome the static friction at a and b. also, find the vertical reactions on each of the two legs at a and at b. the coefficients of static and kinetic friction at a and b are ms = 0.5 and mk = 0.2, respectively

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's