Open Query 21

#$&*

course Phy 121

021. `query 21

*********************************************

Question: `q Explain how to obtain the final speed and direction of motion of a projectile which starts with known velocity in the horizontal direction and falls a known vertical distance, using the analysis of vertical and horizontal motion and vectors.

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution: The horizontal velocity as we know is unchanging, so we’re almost always left to find the vertical quantities first. In the notes we had an angle at which the projectile was launched, a displacement, and an initial velocity. We use this initial velocity to find our x and y components, with our x component being the horizontal velocity, the y component being the vertical velocity. We can’t do much with our x component but with the y component we now have quantities for displacement, acceleration, and initial velocity, which we can use either through the quadratic method of our 3rd equation to find the time interval, or our 4th equation to find final velocity, average velocity, and then time interval. With the time interval we can determine the horizontal displacement.

???Is it imperative under these circumstances that we use the 3rd equation of motion, this reveals two numbers, both of which are useful, but I haven’t checked if the one we really want ends up being the same as the same result obtained from the 4th equation of motion???

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

`a** The horizontal velocity is unchanging so the horizontal component is always equal to the known initial horizontal velocity.

The vertical velocity starts at 0, with acceleration thru a known distance at 9.8 m/s^2 downward. The final vertical velocity is easily found using the fourth equation of motion.

We therefore know the x (horizontal) and y (vertical) components of the velocity. Using the Pythagorean Theorem and arctan (vy / vx) we find the speed and direction of the motion. **

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

In a few examples we were given initial velocity which we then used to find x and y components, but this was under the pretense the projectile was fired at an angle. Here our horizontal velocity is the x component, and the vertical velocity is our y component. Using this we can find the angle and the magnitude of the speed.

------------------------------------------------

Self-critique Rating:

*********************************************

Question: `qGive at least three examples of vector quantities for which we might wish to find the components from magnitude and direction. Explain the meaning of the magnitude and the direction of each, and explain the meaning of the vector components.

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution: Our best examples so far have been force, velocity, and momentum, all of which have direction and magnitude, and therefore can be fitted to a graph and using the properties of vectors we’ve learned we can find other quantities.

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

`a

Examples might include:

A force acting on an object causing it to move in an angular direction.

A ball falling to the ground with a certain velocity and angle.

A two car collision; velocity and momentum are both vector quantities and both important for analyzing the collision..

The magnitude and direction of the resultant is the velocity and direction of travel.

The vector components are the horizontal and vertical components that would produce the same effect as the resultant.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary): ok

------------------------------------------------

Self-critique Rating:

"

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

"

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

#*&!

&#This looks good. Let me know if you have any questions. &#