# Lect07 - Physics 215 Physics for Elementary Education...

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Physics 215 Physics for Elementary Education Instructor: Dr. Mark Haugan Office: PHYS 282 haugan@purdue.edu TA: Mayra Cervantes Office: PHYS 222 mcervant@purdue.edu TA: Jordan Kendall Office: PHYS 222 kendallj@purdue.edu TA: Daniel Whitenack Office: PHYS 136 dwhitena@purdue.edu Office Hours: If you have questions, just email us to make an appointment. We enjoy talking about teaching and learning physics! Notices: Our rescheduled evening midterm exam begins at 8:00pm THIS Thursday (March 3) in SMTH 108

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Interactions and Forces During the past two weeks you have examined the way in which the effect of and interaction between and object and something in its surroundings depends on the direction of the force exerted on the object relative to the direction in which the object is moving when the force acts. Forward Last week, we discussed how this dependence allowed us to explain why some mechanical interactions increase the kinetic energy of the object acted upon by the corresponding force and others decrease it. In the case depicted above, which interaction would increase the cart’s kinetic energy, one producing a forward push or one producing a backward push? Explanatory Narrative: Based on our observations in lab and elsewhere we agreed that when a force acts on an object in the direction it is moving the object speeds up and that when a force acts on an object in the direction opposite that in which it is moving the object slows down. Since an increase in the object’s speed means an increase in its kinetic energy, the forward push is the one that will increase this cart’s kinetic energy.
This week in lab you examined effects of forces exerted on objects by things in their surroundings that act in directions besides forward and backward relative to the object’s motion. Q1. Two taps of about the same strength are applied to a soccer ball as shown in this picture. Which of the three arrows on

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## This note was uploaded on 04/23/2011 for the course PHYS 215 taught by Professor Unknown during the Spring '11 term at Purdue University-West Lafayette.

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Lect07 - Physics 215 Physics for Elementary Education...

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