Projectile fun.

http://www.walter-fendt.de/ph14e/projectile.htm

Play with this and see how your own problems (and calculations) compare to what the applet gives you.

Forget about Angry Birds - this is the real physics!

homework

practice

1.  A soccer ball is kicked at a 40 degree angle with speed of 22 m/s.  Find:

a.  initial components of velocity
b.  time to apogee
c.  total time in air
d.  maximum horizontal displacement
e.  maximum height achieved
f.  If this projectile had been kicked at this angle/speed off a 20-m high cliff, how would the problem change?  You don't have to solve it, but think about how it could be dealt with.

2.  Look up the range equation - it is a useful expression for solving projectile motion problems when trying to determine the maximum horizontal displacement.  When is it useful?

some new problems

These are assigned first for E-block.  Then C-block will have a go at them after Monday's class.

1.  Projectile motion.  Consider throwing a ball horizontally at 30 m/s off a 25-m high cliff.

a.  Find the time to hit the ground.
b.  Find the horizontal distance where the ball lands from the cliff.

2.  Consider a velocity vector of 40 m/s, at an angle of 60 degrees (with respect to horizontal).

a.  Find the x-component (horizontal).
b.  Find the y-component (vertical).

This type of thing will be important when we deal with projectiles launched at angles.

3.  Think about how we might approach the problem of projectiles launched at angles.

For example, if you threw a ball at 20 m/s, with an angle of 30 degrees, how would you find things like the time in air and horizontal displacement?  Try this, or think about how to approach it.

4.  Practice for vectors at non-right angles.  Two vectors, 200 and 500, are separated by an angle of 40 degrees.  Find the resultant vector (c, if you use the law of cosines).

vector hw

The following problems involve vector addition.

1.  You're on a people mover, which itself is moving 3 m/s to the right.

a.  If you run at 2 m/s to the right, what will be your speed relative to an outside observer not on the people mover?

b.  How should you move to "stay in place?"

c.  If you run at 4 m/s to the left, what will be your speed relative to an outside observer not on the people mover?


2.  Two ropes are attached to a large boulder.  One rope is being pulled with a 50 lb force to the East.  Another rope is being pulled with a 75 lb force South.

a.  What is the net force on the boulder?

b.  What angle does this net force make with respect to East?


*3.  A small airplane is flying due SouthEast at 70 m/s.  It is hit by a wind (15 m/s, due South).

a.  Draw this problem.

b.  Assuming that these vectors add concurrently (same place, same time), what will be the resultant vector - magnitude and angle.  You may need to use the law of cosines and/or law of sines.


*4.  Consider a 100 lb force vector, at an angle of 30-degrees with respect to horizontal.  What part of this vector can be considered to be horizontal and what part is vertical?  This is a little tricky, breaking a vector into components.  Make a triangle and set up sin and cos relationships for the vector/triangle.


* these are a wee bit tricky.  Do try them, though.

trig practice

...for those who want/need it.

1.  Consider a 5-12-13 right triangle.  Find the angles.

2.  A right triangle has a 5-m long hypotenuse.  One angle in the triangle is 20 degrees.
Find the other sides.

3.  A "river problem."  A toy motorboat heads south across a 20-m stream.  The current
in the stream is flowing at 2 m/s toward the west.

a.  Draw this problem.
b.  Find the time to cross the stream.
c.  Determine where the boat lands.


ALSO - DON'T FORGET THAT THE MOTION QUIZ IS DUE AT THE BEGINNING OF THE NEXT CLASS.

awesome.

http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734