Page 5
This text is meant to accompany class discussions. It is not everything there is to know about uniform circular motion. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)

Click for the questions that go with this reading
Determining Direction for Motion in a Plane

In order to determine the direction, you need to know right triangle trigonometry.

Trig Review

Do the review if its been a while since you have used sine, cosine, and tangent.

 

To find the direction of a projectile, use kinematics to find the vertical velocity, Vx, and the horizontal velocity, Vx, at a position along the path. Use these two components to create a triangle. Then use trigonometry to calucalate the direction.

 

Example 1
A ball is thrown off the top of a cliff with an initial vertical velocity if 4.00 m/s upwards and with a horizontal velocity of 6.00 m/s. Neglect air resistance. Vertically the ball experiences the acceleration due to gravity. Horizontally the ball is moving at a constant velocity. What is the direction and speed of the ball after 4.00 seconds?
Solution
YouTube version of the example's solution, http://youtu.be/gC2xQ6FAHDA It will open in a new window.

 

Example 2
A ball is thrown off the top of a cliff with an initial vertical velocity if 4.00 m/s upwards and with a horizontal velocity of 6.00 m/s. Neglect air resistance. Vertically the ball experiences the acceleration due to gravity. Horizontally the ball is moving at a constant velocity. After some unknown number of seconds the ball is 62.4m below the starting point and 24 m to the right. What is the ball's direction and speed?
Solution
YouTube version of the example's solution, http://youtu.be/eFjFkVtT14s. It will open in a new window.

 

 


by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)