Open Query 21

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course PHY 121

4.15.11 at 9:50pm

021. `query 21

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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.

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Your solution:

Vertical motion will likely be 0. YOu first need to find vf by using vf^2 = vo^2 + 2a'ds. Using the given horizontal direction, you have just found the vertical direction and have the x and y componentand are now able to find the magnitude as well as the direction.

Magnitude of vf = sqrt(x^2 + y^2)

direction = arctan(y/x) + 180 (if x is negative)

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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. **

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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.

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Your solution:

Velocity, vector components are horizontal and vertical direction

Acceleration, vector components are 'dt and 'dv

Displacement, vector components are 'dt and vAve.

Not sure what you are asking with the rest of this problem.

confidence rating #$&*:

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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 directiohn of the relsultant 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.

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&#Your work looks very good. Let me know if you have any questions. &#