What is the mass in kilograms of a copper pipe that weighs 12.5 pounds? (1 lb = 453.6 g)?

To solve this problem we will apply the concepts of conversion. We will simply carry the value of pounds to kilograms, so from the statement we have the equivalent:

Now if 1 lb is equivalent to that value, 12.5 lb would be

Note that the values are available in this order and the units are also canceled and the kilograms are maintained.

heats surface water up

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.