Homework solution part 1



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Read before next class, if you have time.

MOMENTUM! We come up with momentum through Newton's 2nd Law: F = ma F = m  D v/t Rearranging: Ft = m  D v So this means that (on the left side) Force x time = (on the right side) mass x change in speed. Or simply: Ft = mv This interaction of force happens during a so-called "collision" or "explosion". Ft is defined as "impulse" and mv is defined as "momentum."   Note that the above equation helps explain how boxing gloves and airbags work – they increase the time of contact, thereby decreasing the average force delivered to the object. Please watch these clips: https://www.youtube.com/watch?v=3vDQm0qIYi0 https://www.youtube.com/watch?v=y3InF19dzlM Momentum  (which is the mv part of the above equation) is another way to describe (mathematically) how objects collide or explode – generally involving contact of some sort. p = mv No new unit here, just:   kg-m/s Momentum is...
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For Wednesday's class

This homework is related to the discussion we had in class about horizontal motion vs. vertical motion. A baseball is thrown horizontally at 30 m/s (which is a pretty typical Park pitcher throwing speed).  It leaves the pitcher's hand 1.5 m above the ground. 1. How long would the ball take to hit the ground, if it does not hit a bat (or anything else) first?  Keep in mind this is just like a dropped object, since there is no horizontal acceleration for the ball (after it leaves the pitcher's hand). 2.  How far will the ball travel horizontally in this time.  Hint:  use v = d/t (since there is no horizontal acceleration). 3.  Is there any time difference between this thrown ball and another ball dropped from the same height (instead of thrown)?  Discuss why. 4.  Challenge question.  If the pitcher were standing on a 0.5 m tall mound,  but otherwise throws as above, how long would the ball take to touch ground and how far would i...
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Homework for Tuesday's class

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A runner stars from rest and accelerates at 0.5 m/s/s for 10 seconds. If using the equations of motion is still tricky for you, be sure to set up the 4-step process: - What is known? - What are you looking for? - What is a relevant equation? - Solve it. 1.  What is her velocity after 10 seconds? 2.  How far does she go in this time? 3.  What would a graph of her distance vs. time look like?  Draw a rough approximation. 4.  What would a graph of her speed vs. time resemble?  Draw a rough approximation. Here is a reminder from today's class:
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