1. The problem statement, all variables and given/known data Laura propels a stone straight up with her slingshot. The stone strikes a tree branch 4.0m above her. It strikes the branch with a velocity of 5.0m/s. How long does this take? a= -9.81 m/s2 v1 = 5.0m/s d= 4.0 m 2. Relevant equations d=vit+1/2at2 d=v1+v2/2 x t v2=v1+at 3. The attempt at a solution ATTEMPT 1: DOESN'T WORK I believe I should use d=vit+1/2at2 therefore: 4m = (5.0)(t)+1/2(-9.81)(t)2 -4.91t2 + 5.0t -4 =0 However I can't do this because using quadratic I get a negative. Therefore it's not an option. ATTEMPT 2: CAN I ASSUME v2=0? d=v1+v2/2 x t 4=(5)+ (0)/2 x t t = 1.6s * But I guess I can't assume the V2=0 Attempt 3: CAN I ASSUME v2=0? v2=v1+at 0=5 +(-9.81)t t = 0.51 s. I know the answer is 0.53s, however how do I know whether I should use attempt 2 or attempt 3? I know to use attempt 3 because it's the right answer, but in my mind 1.6 s makes sense too. Please help!