According to Israel’s Home Front Command guidelines, when you hear a rocket siren , you should immediately move to a safe area, a nearby building or the stairwell of your building and remain there for at least 10 minutes. If none of these options is nearby, lie flat on the ground and shield your head with your hands for a similar duration. The reason for this specific timing is that it can take a while for shrapnel of intercepted rockets or missiles to reach the ground.
Home Front Command explains 10-minute wait rule after rocket sirens to avoid debris risks Prof. Iair Arcavi, a faculty member at the Raymond and Beverly Sackler School of Physics and Astronomy at Tel Aviv University, explains that after Israel’s air defense systems intercept an incoming threat, the resulting fragments initially fall to the ground in freefall. However, within seconds or minutes, air resistance begins to play a significant role.
“The fragments encounter drag, which acts as a counterforce to gravity, increasing with speed. This reduces the acceleration of their fall compared to true freefall until they reach a constant terminal velocity,” says Prof. Arcavi.
He adds that various factors, like air currents or winds, can further slow down the fragments’ descent. Interestingly, larger fragments can sometimes take longer to fall than smaller ones. While many assume that heavier fragments fall faster, the opposite is often true due to increased air resistance.
Prof. Arcavi cites Galileo Galil.
