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Pendulum homework for Monday

In these problems you will need the formulas for the period of a simple pendulum AND the rearranged version (solving for L) we worked out in class. 1.  What is the period of a 1-m long pendulum?  Do you remember the historical significance of this particular length of pendulum?  If not, look back in your notes from the first few days of class. 2.  If you want a Grandfather clock to swing with a 1-second period, how long should the pendulum be inside of it? 3.  Calculate the experimental length of the giant swing, assuming that someone took 2.8 seconds to swing from rest on the platform to the opposite side of the swing (on the left).
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HW related to pendulum lab

1.  Graph period of ONE swing (T, in seconds) vs. length (L, in meters).  T will be on y-axis and L will be on x-axis.  Make certain that length is converted to meters (if you used cm). 2.  Print out graph. 3.  Make a third column of data - square root of each length measurement (in meters). 4.  Think/write about this:  What makes a simple pendulum "simple"?  What is assumed to be true about the simple pendulum? 5.  If you have the video from the giant swing, try to determine the period of one oscillation (one complete swing of the person).  We are going to try to compare theoretical pendulums to the giant swing in our next class.
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Momentum practice problems (answers included)

Review the notes on the blog (2 posts ago) and try these questions and problems (similar to what we did in class today, Monday 4/2). 1.  Give an example of 2 different conservation laws. 2.  What is the mathematical definition of momentum? 3.  What is the conservation of momentum, and when do we think about it (under what specific circumstances)? 4.  A 300-g cart moving at 40 cm/s hits another 300-g at rest.  Friction is very low.  What do you expect will happen exactly?  Give numbers if possible. 5.  A 60-kg figure skater skating at 8 m/s collides directly with a 40-kg skater initially at rest.  Friction is very low and the two become intertwined on the ice.  Calculate the speed of the two of them together after the collision.  (Hint:  First find the momentum of the 60-kg skater, and then use conservation of momentum to solve for the final speed of the two together.  This is like the velcro cart collisions.) 6.  (Challenge problem)  A 2-kg ball is traveling at 4 m/s and it
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Wonderful to watch

https://youtu.be/HSLxNHPVtxY See also the previous blog post, for reading if you have time.
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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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HW for Monday

Solve these problems using the energy concepts. 1.  A lacrosse ball (0.15 kg) is thrown straight upward at 14 m/s.  How high does it go (max height)? 2.  A brick of unknown mass is dropped from 3-m above the ground.  Find the speed it has right before hitting the ground.  (Recall that the mass does not matter - show this in the calculations.)
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practice problems for energy - to do for Wednesday's class

These will NOT be collected, but an assignment given Wednesday afternoon WILL be collected during class on Friday. 1.  Define energy. 2.  Define PE and KE . 3.  What is the conservation of energy principle? 4.   Consider a 5-kg bowling ball that has been raised to 2-m above the ground.  Find the following: a.  initial PE b.  final KE right before it hits the ground c.  PE and KE right in the middle of the drop (1-m above the ground) d.  speed right before hitting the ground - treat this as an energy problem e.  does the mass matter for part d?  Explain. You may let g = 10 m/s/s for this problem, if you like.
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