Relative to an observer on the boat, her speed is Ĭonsider the scenario when Emily is walking in the opposite direction. Relative to an observer on the boat, her speed is. Ĭonsider the scenario when Emily is walking along with the boat. We multiply by and then add to get from whichĬall the speed of the boat and the speed of Emily. When Emily walks from the back of the ship to the front, she walks a distance of and the front of the ship moves a distance of We have for this scenario, which rearranges to When Emily walks in the opposite direction, she walks a distance of and the back of the ship moves a distance of We have for this scenario, which rearranges to Let be the length of the ship, be Emily's step length, and be the ship's step length. Suppose that Emily and the ship take steps simultaneously such that Emily's steps cover a greater length than the ship's steps. We can equate the expressions for and solve for : We can create a similar equation: Now we have two variables and two equations. Walking in the opposite direction of the ship, it takes her steps, or hour. We can create an equation: where is the length of the ship. Walking in the direction of the ship, it takes her steps, or hours, to travel. Let the speed at which the ship is moving be. Let the speed at which Emily walks be steps per hour. Dividing both sides by and cross multiplying, we get, so, and. Since the ship and Emily both travel at some constant rate.
Then, in the time that Emily walks steps, the ship moves steps.Īlso, in the time that Emily walks steps, the ship moves steps. In terms of Emily's equal steps, what is the length of the ship? Walking in the opposite direction, she counts steps of the same size from the front of the ship to the back. She counts equal steps walking from the back of the ship to the front. She walks parallel to the riverbank at a uniform rate faster than the ship. Links provided to third-party sites are not under Coinbase control, and Coinbase is not responsible for content on such third-party sites.Emily sees a ship traveling at a constant speed along a straight section of a river. Information on this page is intended for and directed to customers in the United States only. Securities and Exchange Commission or the U.S. Coinbase makes no representation on the accuracy, suitability, or validity of any information provided. This is not a recommendation to buy or sell a particular digital asset. Information is provided for educational purposes only and is not investment advice.
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