A5.10-kg watermelon is dropped from rest from the roof of a 24.0-m -tall building and feels no appreciable air resistance.
calculate the work done by gravity on the watermelon during its displacement from the roof to the ground.
part a
calculate the work done by gravity on the watermelon during its displacement from the roof to the ground.
part bjust before it strikes the ground, what is the watermelon's kinetic energy?
part cjust before it strikes the ground, what is the watermelon's speed?
part dwould the answer in part a be different if there were appreciable air resistance?

Part a)

Part B)

Part C)

Part D)

no change in answer of part A) if there is air resistance in that problem.

Explanation:

Part A)

Work done by the gravity is given as

now we have

m = 5.10 kg

H = 24 m

now we will have

Part B)

As per work energy theorem we can say that work done by all forces = change in kinetic energy of the system

So we will have

Part C)

Now we know that the kinetic energy is given as

Part D)

Work done by gravity only depends on force due to gravity and its displacement so there will be no change in answer of part A) if there is air resistance in that problem.

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.