Select the correct answer. A young man sets goal to compete in marathon in two weeks. He started training last week by exercising three to four times a week with his friend. After each
training session he writes his daily experiences to assess problems that may hinder his achievements. What aspect of his fitness program could keep him from
achieving his goal?

carla slowed down in the beginning of her trip, stopped, and then sped 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.

b. false

explanation:

suppose a rock in free fall is dropped off a cliff. after falling for 5 seconds, its speed would not be 100 m/s.