To create an impact equivalent to 4kg using a 70g weight in a vacuum, the required altitude is indeterminate and depends on various factors, including the rigidity of both the dropped object and the target. The force of 40 Newtons is necessary for the impact, which translates to a deceleration rate of approximately 571 meters per second squared, significantly exceeding Earth's gravity. For rigid objects, this acceleration could be achieved from a drop of less than 1cm, while softer objects would require a greater height. Estimating the height involves comparing the deflection at impact to the drop height, suggesting a ratio of 57 times the deflection. Ultimately, predicting the exact impact force is complex due to the numerous variables involved.