Question

A student is testing the kinematic equations for uniformly accelerated motion by measuring the time it takes for light-weight plastic balls to fall to the floor from a height of 3 m in the lab. The student predicts the time to fall using g as 9.8 m/s^2 but finds the measured time to be 35 % greater. Which of the following is the most likely cause of the large percent error?

a) the acceleration due to gravity is 70% greater than 9.8m/s^2 at this location
b) the acceleration due to gravity is 70% less than 9.8 m/s^2 at this location
c) Air resistance increases the downward acceleration
d) the acceleration of the plastic balls is not uniform
e)the plastic balls are not truelly spherical.

Well I think e) could be true but a bit unlikely. I think that d) would be wrong because 9.8m/s^2 is constant. So it leaves either a) or b). I believe it’s b) since it would take longer for an object to fall it acceleration is less.

The only answer that makes any sense is (d). The downward acceleration decreases as air resistance increases.

Air resistance DEcreases the downward acceleration. The part of the acceleration that is due to gravity does not change.