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

what did joule's experiment directly show?

the temperature of water increases from the addition of heat.

heat is a form of energy.

heat can be neither created nor destroyed.

electromagnetic radiation has energy

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.