Lois and Clark live in a high-rise apartment building. Lois lives on the 30th fl

Question

Lois and Clark live in a high-rise apartment building. Lois lives on the 30th floor, and Clark lives on the 32nd floor directly above her. When Clark was visiting Lois, he left his cell phone in her apartment. When she finds it, she calls him through the window. Forgetting what a klutz he can sometimes be, she throws the cell phone straight up to him with an initial speed of 20.0 m/s. But being the klutz that he is, he misses catching the phone both on its way up, and again as it is falling down. Meanwhile, Jesse is walking along when he realizes what's going on. The instant that he sacs Clark miss catching the phone for the second time on its way down, he starts to run to see if he can catch the phone before it hits the ground. If Jesse is a distance of d = 25.0 m away at the instant Clark misses the phone for the second time as it's falling, how fast must he run to just catch the phone before it hits the ground? Jesse, too busy running as fast as he can, didn't notice that when the phone passed Lois on its way down, she tried to reach out and catch it. Unfortunately, she reached too far and fell out the window. Clark notices Lois fall out the window and is horrified. It takes him 1.70 s to change into his Superman uniform to try to catch Lois. Assuming he jumps out the window with zero velocity and then accelerates with a constant downward acceleration, what was Superman's acceleration if he caught Lois 5.00 m before hitting the ground? After Jesse catches the phone, he continues running for a bit with constant velocity. Meanwhile, after catching Lois, Superman decelerates to make a perfectly smooth landing on the ground at zero velocity. What must Superman's deceleration be in order to make sure Jesse is at least 2.00 m past them when they land? Lois throws Clark's cell phone up to him. Jesse is a distance, d, away when Clark catching it. (b) After Lois falls out the window, Superman dives down to save her. (Not to

Explanation / Answer

intial speed of phone when it is thrown = 20 m/s

speed of phone when it misses clark for second time U = ?(202 - 2*g*5.5 ) = 17.1 m/s

now time taken by phone to reach ground be t

90.5 = Ut + 0.5gt2

4.9t2 + 17.1t - 90.5 = 0

t = 2.9 sec

speed of jesse = distance covered by jesse /time = 25/2.9 = 8.6 m/s

2)

when lois falls time taken by her to reach ground t = ?(2h/g) = 4.1 sec

since superman starts after 1.7 sec he should reach ground before 2.4 sec

so min accleration = 2h/t2 = 2*90.5/2.42 = 31.4 m/s2

3)

distance of jesse and superman = speed*time difference = 8.6*(4.1-2.9) = 10.32 m after crossing the building

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