Answer:
The vertical acceleration is -9.81 m/s^2
Step-by-step explanation:
When a body is projected, the body experiences an acceleration in the vertical axis that is proportional to the acceleration due to gravity of the earth, which is equal to 9.81 m/s^2. In this case, the acceleration acts to stop the vertical motion of the paper plane, and hence is a deceleration, which explains the negative vertical acceleration.