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Introductory Physics Homework Help
Finding the time when two stones cross paths
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[QUOTE="Ace., post: 4664996, member: 449486"] [h2]Homework Statement [/h2] Two stones are thrown simultaneously, one straight upward from the base of a cliff and the other straight downward from the top of the cliff. The height of the cliff is 6.69 m. The stones are thrown with the same speed of 9.97 m/s. After what time do the stones cross paths? [h2]Homework Equations[/h2] d = vt + 0.5at[SUP]2[/SUP] [h2]The Attempt at a Solution[/h2] distance traveled by both rock A and rock B combined is 6.69 D[SUB]A[/SUB] + D[SUB]B[/SUB] = 6.69 let the upwards direction be positive D[SUB]A[/SUB]: (top of cliff) d = v[SUB]i[/SUB]t + 0.5at[SUP]2[/SUP] = (-9.97 m/s[up])t + 0.5(-9.8 m/s[SUP]2[/SUP][up])t[SUP]2[/SUP] = -9.97t - 4.9t[SUP]2[/SUP] D[SUB]B[/SUB]: (base of cliff) d = v[SUB]i[/SUB]t + 0.5at[SUP]2[/SUP] d = (9.97 m/s [up])t + 0.5(-9.8m/s[SUP]2[/SUP][up])t[SUP]2[/SUP] d = 9.97t - 4.9t[SUP]2[/SUP] D[SUB]A[/SUB] + D[SUB]B[/SUB] = 6.69 -9.97t - 4.9t[SUP]2[/SUP] + 9.97t - 4.9t[SUP]2[/SUP] = 6.69 -9.8t[SUP]2[/SUP] = 6.69 getting negative time...? t = 0.82 s the correct answer is 0.335 seconds. I think I am messing up my directions and signs for my vectors... any help? [/QUOTE]
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Introductory Physics Homework Help
Finding the time when two stones cross paths
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