As objects fall, they increase their speed due to the force of gravity. air resistance counteracts gravity's pull by resisting the downward motion of the object. the amount of air resistance depends on several factors, the two most important being are the speed of the object and the cross-sectional area of the object. when the amount of upward air resistance force is equal to the downward gravity force, the object encounters a balance of forces and is said to have reached a terminal velocity. the terminal velocity value is the final, constant velocity value achieved by the falling object.

a group of students were investigating the force of gravity and air resistance. they began by dropping a foam ball from a height of 3 meters into a bucket of sand. the ball hit the sand in 0.306 seconds. they dropped additional balls of approximately the same diameter, but of different masses.

one interesting observation made by the students was that the greater the mass of the ball, the deeper the indentation in the sand. here is the data they collected. next the students dropped a large index card which hit the ground in 1.05 seconds. they added two index cards for each successive drop and got the following data.

how can this data you determine what statements are true? (multiple answers)

- the balls all fell at about the same velocity
- decreasing the amount of air resistance will increase the velocity of a falling object
- Consider F=ma. if acceleration due to gravity (a) is constant, then the balls hit the sand with varying amount of force (F).
- increased cross-sectional area of the index cards accounted for the increased air resistance.
- in a vacuum, paper would have fallen faster than any of the balls.
- the foam and hollow plastic balls experienced more air resistance than the baseball or solid wooden ball.