A 1 kg block is placed near the top of an inclined plane that is at an angle of 30 degrees with respect to the ground, as shown above. By
correctly determining the effect of gravity, a student predicts that the acceleration of the block will be 5 m/s². After allowing the block to
slide down the inclined plane, the student finds that the acceleration is actually 4 m/s². What type of force did the student most likely not
account for when predicting the acceleration of the block, and what is the magnitude of that force?