Answer:
Acceleration of the platform = - 1.8 m/s²
Explanation:
The net force acting on a body accelerates the body in the same direction as that in which the resultant is applied.
Writing the force balance for the setup,
ma = 800 - mg
100a = 800 - 100×9.8
100a = - 180
100a = - 180
a = - 1.8 m/s²
This means the body falls downwards.