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.

The air resistance decreases the downward acceleration. Therefore, due to air resistance exist when the ball speed up, downward acceleration decreases. It makes that acceleration of the plastic ball not uniform. This is the reason why measured time is 35 % greater.

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