135 reputation
3
bio website
location
age
visits member for 2 years, 10 months
seen Apr 7 at 21:09

Mar
1
comment Freefall into snow
Deceleration may be constant over its path through the snow, but as implied above, a) the path may be very short, much shorter than 4 m - hence not uniform over 4 m of compression, which is what I meant, implying much higher deceleration, or b) constant over 4 m, then extremely high as they hit solid ice. It's very unlikely that the properties of snow and the velocity of the heroes is such that it'll take exactly 4 m to decelerate to zero. Hence all you have is a lower limit.
Feb
26
comment Freefall into snow
Why do you assume that deceleration is going to be in any way uniform? The snow doesn't "know" that it's going to take 4m to decelerate, even if the snow is uniform density. They could decelerate to zero in the top 10 cm, or they could be still falling at nearly full speed when they've penetrated 4 m, then come to a sudden crushing halt. I wouldn't say your answer makes it in any way plausible; it just places a lower limit on the maximum acceleration, and showing that it's not impossible based on the distance alone. It doesn't tell us anything about how high the acceleration will be above 9.5G
Feb
25
accepted Velocity increase calculated from kinetic energy in different frames
Feb
25
comment Velocity increase calculated from kinetic energy in different frames
Yeah it wasn't about planes specifically, but "the air" in this case fills the role of the other object that has to take the other half of the momentum, which is what I neglected. The question doesn't work without anything accelerating, because then the kinetic energy wouldn't have changed. Anyway, I understand now. Very helpful!
Feb
25
revised Velocity increase calculated from kinetic energy in different frames
added tag
Feb
25
asked Velocity increase calculated from kinetic energy in different frames
Oct
2
awarded  Scholar
Oct
2
accepted Can a neutron be created from pure energy
Sep
20
awarded  Supporter
Sep
19
awarded  Student
Sep
19
asked Can a neutron be created from pure energy