Retard Chama
Landing time is irrelevant as the question states the distance in which the phone drops from A-chan and the speed in which A-chan travels from the point of droppage. 12 m of separation, she moves at 2m/s so it takes 6 seconds from the phone dropping to reach it. If were going by the problems stated timeline the phone is reached at t=9.
TL;DR Relativity
(Likely intended phrasing that also makes your answer correct: B-san drops his smartphone, with it hitting the ground at t=3s)
A-chan and B-san are walking in the same direction at a constant speed of 1.5m/s and are 12m apart. At t=3s, B-san drops his smartphone.
How much time it takes for A-chan to reach B-san's phone? [From the time of the drop]
[No additional velocity is imparted from the drop.]
[All velocities with reference to the ground, air resistance ignored.]
Between the act of dropping the phone, and
before the phone hitting the ground, the phone follows B-san's velocity of 1.5m/s.
For that period A-chan only closes in on the phone at a rate of only 0.5m/s = (2m/s - 1.5m/s). (Instead of the assumed 2m/s throughout)
Only
after the phone hits the ground, does its velocity get to 0m/s [bouncing, rolling, friction etc. ignored], allowing A-chan to close in on it at the full 2m/s.
Therefore, the longer the drop, the more time it's going to take to reach the phone.
To be clear,
if they were to both keep moving at the same speed without speeding up, A-chan would never actually even
start to close in on the phone,
until the phone hits the ground.
(See: Relativity, any “throwing balls on a car” or “dropping things in a train” experiment.)
(A mythically tall man could, if she speeds up after the phone was released, drop the phone right into her hands, or even behind her, and given the question uses "speed" instead of velocity, that's even more ways to mess with the wording, but I considered that too far even for a shitpost.)
The question has a typo it obviously means to say 2.3m/s. Also it doesn't require us to know how long she speeds up for 2.3m/s as it goes until she catches up with him so let's break it down for your retard brain. She reaches the phone at t=9. She takes 2 seconds to pick it up so t=11. Then it takes her 3 and (21/23) seconds to catch up to the stranger so t=14(21/23). The 5 seconds it takes to get his attention are irrelevant to the problem.
TL;DR Acceleration
(Likely intended phrasing that also makes your answer correct: then instantly accelerated to 2.3m/s)
then speeds up again [from standstill] to 2.3[m]/s [at some point in time] to catchup to B-san
The speed throughout matters, not just attaining it at some unspecified point in time.
(See: 0-60 times for cars, drag races etc.)
Her accelerating linearly (or otherwise) up to the point of catching up, with the speed of 2.3m/s at said point (or even any point in-between) still fulfills the question as written while giving different results, albeit being harder to calculate.
(I was going to make the bit about how any instant changes in speed requires infinite acceleration, which isn't possible, and how even if theoretically achieved, could be deadly. But given the possible thought of having to consider how elasticity might be a mitigating factor against the (albeit impossible) scenario, I decided to go for the lower hanging fruit instead.)
IT IS STATED femboy LEARN TO READ! She takes 2 seconds to pick up the phone, implying she is not moving that is the point of mentioning the time in which she picks it up is that it interrupts her movement! They wouldn't mention it otherwise.
TL;DR I was being a dick
(Likely intended phrasing that also makes your answer correct: spends 2s to stop, and picks up the phone before (…))
(I actually can’t find her coming to a stop being explicitly stated anywhere.)
Other than (me) sidestepping the obvious implication, the second frame has her bent down picking up the phone with the “<- 2m/s” being shown at the same time, which I used to construe her still walking, even while bending down to pick up the phone.
I also tried not to pick on the ESL stuff that didn't really affect the question, only omissions of information or phrasing that allowed for other interpretations. (Except once, at "1c) base[d]", hinting at the question being ESL, but I didn't make the point about it either.)
