HW for Wednesday (F) and Thursday (A)

F:  These are the problems that were on the board yesterday.  Nothing new here.

1.  Consider a ball kicked off a 30-m tall cliff with an initial speed of 20 m/s.  How long does it take to hit the ground below?  (The quadratic formula, if you know how to use it, makes this problem a bit easier - or at least, then it can be done in step.)

2.  The drowsy cat.  A cat sits on a window sill (2-m in height).  It notices that a flowerpot sails up and past the top of the window (still moving up), then down and past the cat again (still moving down).  The total amount of time that the flowerpot is in sight is 1/2 a second (1/4 up and 1/4 down). How high ABOVE the top of the window frame does the flowerpot travel?  (Yes, this is a tricky problem.)

3.  Bonus, slightly less tricky problem.  A ball falls from rest.  It takes 1 second to fall the second half of its path downward.  From what height was it released and how long was it in air?

Reminder

Lab draft due and brief quiz next class (Friday A, Monday F)

HW for Monday (A) and Tuesday (F)

Use the equations of motion (where helpful) to solve the following problems.

1.  Consider a sports car, capable of accelerating from rest at 5 m/s/s.  If it accelerates uniformly for 8 seconds, find:

a.  the velocity after 8 seconds
b.  how far the car has gone in this time

Now assume that the driver applies the brakes and the car uniformly comes to a halt in 3 seconds.

c.  What is the acceleration during this braking time?
d.  How far does the car go during this time?

Draw two graphs that represent:

a.  the displacement vs. time for the entire trip
b.  the velocity vs. time for the entire trip


2.  Imagine that a falling body accelerates at 10 m/s/s.  It is released from a high tower:

a.  If it takes 3.5 seconds to hit the ground, how fast is it traveling immediately before hitting the ground?
b.  If it took 3.5 seconds to hit the ground, how tall was the tower from which it was released?

Keep working on your lab report.  Expect a draft to be due by Friday.

HW

As mentioned in class:

Use Google maps, etc. to "map out" your trip to school.  Find the following:

distance

time - you should probably use your own approximate time to school in the morning.  Convert to hours (dividing minutes by 60)

displacement - measure on the screen (start to end) and use the scale to convert to miles

Then calculate:

speed
velocity

Please work in miles and hours.