Bill and Brenda are building a house. Bill is standingon the ground, and Brenda

Question

Bill and Brenda are building a house. Bill is standingon the ground, and Brenda is standing on the second storyscaffolding 18 feet Bill. a. If Bill throws a tape measure up to Brenda, with whatintial speed must he throw it for it to just reach Brenda? b. Suppose the tape measure reaches the correct height butBill misses catching it. How long does Brenda (on the ground)have to get out of the way before the tape measure hits the groundwhere she is standing? Bill and Brenda are building a house. Bill is standingon the ground, and Brenda is standing on the second storyscaffolding 18 feet Bill. a. If Bill throws a tape measure up to Brenda, with whatintial speed must he throw it for it to just reach Brenda? b. Suppose the tape measure reaches the correct height butBill misses catching it. How long does Brenda (on the ground)have to get out of the way before the tape measure hits the groundwhere she is standing?

Explanation / Answer

a. This is a simple 1-d motion problem. Usev2=vo2+2ax, where a isacceleration due to gravity (in this case -32.2ft/sec) and v is thefinal velocity, 0 in this case. Because of this, you getvo2=2ax (since a is negative). Thenvo2=2(32.2)(18)=1159.2. Sovo=34.05 ft/s. b. Here, you are going to want to use v=vo+at. v isagain going to equal 0. so vo=at. So 34.05 (from a) =32.2t. 34.05/32.2=1.057. Then you double 1.057 (because that is thetime going up, and it takes equal time up and down) for a finalanswer of 2.11 seconds. Hope this helps!

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