Final answer:
The necessity of two employees for safety when using a hand truck depends on workplace guidelines; the need is not absolute. In a tug-of-war event, equal and opposite forces are at play until the rope snaps. The boy pushing a box up a ramp does not necessarily exert a force of exactly 100 N due to the mechanical advantage of the ramp.
Step-by-step explanation:
The original question posed was whether two employees are necessary for safety when using a hand truck to load or unload a van. Official safety protocols and guidelines often emphasize the importance of a two-person team for such tasks to prevent accidents and injuries. However, the specific requirement can vary depending on the workplace, the weight of the items, and the employer's safety procedures. Without explicit context indicating that it is a safety standard in this scenario, the statement could be considered false, but always consult actual workplace guidelines.
In the case of the tug-of-war, when the rope snaps, the forces involved before the snap were equal and opposite. This is why neither team was moving significantly towards the other team's side. When the rope breaks, the sudden absence of tension would result in both teams falling backward.
Regarding the boy pushing a box up a ramp, it is false that he had to be pushing with a force of exactly 100 N. The actual force required to push the box could be less than the weight of the box (300 N) due to the mechanical advantage provided by the ramp. The force exerted depends on factors such as the ramp's angle, friction, and the efficiency of the energy transfer.