A child slides down a playground slide. If the slide is 3 m high and the child weighs 300 N, how much potential energy does the child have at the top of the slide

Explanation:

Gravitational potential energy = mgh where m is mass , g is acceleration due to gravity and h is height .

mg = weight so

Gravitational potential energy = weight x h ( height )

Putting the given values

Gravitational potential energy = 300 x 3

= 900 J .

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.

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it