I did a lab where and got an acceleration of about 2.13 m/s squared [E] and the theoretical acceleration is about 9.7 m/s squared [E]. The error percentage is 78 percent and my teacher said that a 10 % error margin is good but other than that i need to justify what could of increased the percentage error. Does any one have any general thoughts from previous experiences?

The lab I did was about placing a 1m tape through a spark meter and then send it down an air track.