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Ch 03: Motion in Two or Three Dimensions

Chapter 3, Problem 3

Crickets Chirpy and Milada jump from the top of a vertical cliff. Chirpy drops downward and reaches the ground in 2.70 s, while Milada jumps horizontally with an initial speed of 95.0 cm/s. How far from the base of the cliff will Milada hit the ground? Ignore air resistance.

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Welcome back everybody. We are at the top of a very tall building. And first we drop a rock from that building and we are told that the time it takes for this rock to reach the bottom is 3.2 seconds. Right after letting that rock drop, we are actually going to shoot a ball out horizontally from the building and we are told that it has an initial velocity of 1.9m/s. Now, once it leaves the building, it's actually going to be in freefall and follow projectile motion. And we are asked to find distance away from the building that the ball lands well from our kingdom attic equations were told that the change in our position is given by our velocity Times our time. But what is this time? Right? What we're told that the time that a rock takes to get to the bottom is 3.2 seconds. Now, we must point this out for both the ball and the rock. The only acceleration that is acting on each of these items is the vertical acceleration due to gravity, meaning that since it took 3.2 seconds for the rock to hit the ground, this is going to be equal to how long it takes for the ball to hit the ground, meaning that the time for the ball to hit the ground is also 3.2 seconds, meaning we can use this time in our equation. So let's go ahead and do that. We have that delta X. Is equal to our initial velocity times our time. We have 1.9 times 3.2, Which when we plug into our calculator gives us 6.08 m corresponding to our answer choice b. Thank you guys so much for watching. Hope this video helped. We will see you all in the next one.
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