Physics Help Forum Help with practice exam

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Oct 10th 2017, 08:59 AM #1 Junior Member   Join Date: Oct 2017 Posts: 1 Help with practice exam I have an exam coming up and I don't even know where to begin with this problem. Any help is appreciated A teacher rides in an elevator that moves upwards at a constant velocity and holds a set keys 1.00m above the floor of the elevator. After 2.00 seconds of moving upwards from the ground level of the science building, the teacher releases the keys from their hand. Relative to the ground level of the building, he keys strike the floor of the elevator at the exact height as where they were released. (a) [7 pts] Qualitatively sketch, on the same graph, the vertical position (height) of both the keys and the elevator as a function of time starting from the ground level until some time after the keys hit the floor. Indicate which curve corresponds to the elevator and which corresponds to the keys. Label the point when the keys are released. (b) [4 pts] Describe the motion of the keys and the motion of the elevator shown in your position (height) vs. time graph in part (a). (c) [8 pts] Calculate the velocity of the elevator. (d) [6 pts] Now consider the elevator as traveling downwards at the same constant speed found in part (c). The keys are again released 1.00m above the floor of the elevator. What is the difference in height (relative to ground level) between where the keys are released and where they hit the floor of the elevator? (e) Bonus: [5 pts] Sketch the vertical position (height) of both the keys and the elevator as a function of time during the downward motion described
 Oct 11th 2017, 06:31 PM #2 Senior Member     Join Date: Aug 2008 Posts: 113 keys position & elevator floor position both height in meters vs time in seconds Attached Thumbnails
Oct 19th 2017, 10:35 AM   #3
Junior Member

Join Date: Jul 2017
Posts: 6
 Originally Posted by mdavies23 I have an exam coming up and I don't even know where to begin with this problem. Any help is appreciated A teacher rides in an elevator that moves upwards at a constant velocity and holds a set keys 1.00m above the floor of the elevator. After 2.00 seconds of moving upwards from the ground level of the science building, the teacher releases the keys from their hand. Relative to the ground level of the building, he keys strike the floor of the elevator at the exact height as where they were released. (a) [7 pts] Qualitatively sketch, on the same graph, the vertical position (height) of both the keys and the elevator as a function of time starting from the ground level until some time after the keys hit the floor. Indicate which curve corresponds to the elevator and which corresponds to the keys. Label the point when the keys are released. (b) [4 pts] Describe the motion of the keys and the motion of the elevator shown in your position (height) vs. time graph in part (a). (c) [8 pts] Calculate the velocity of the elevator. (d) [6 pts] Now consider the elevator as traveling downwards at the same constant speed found in part (c). The keys are again released 1.00m above the floor of the elevator. What is the difference in height (relative to ground level) between where the keys are released and where they hit the floor of the elevator? (e) Bonus: [5 pts] Sketch the vertical position (height) of both the keys and the elevator as a function of time during the downward motion described
What needs to be noticed that due to the constant speed of both keys and elevator, relative gravity force on keys over the elevator remains sand as they were not moving.
Let us know whether you can proceed with the given solution (graph) by member above.

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