#$&*
phy 201
Your 'cq_1_19.3' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** **
An object moving in the direction 120 degrees (as measured counterclockwise to the positive x axis) encounters a net force whose direction is 270 degrees.
Sketch the force and its component along the line of motion, as well as its component perpendicular to the line of motion.
answer/question/discussion: ->->->->->->->->->->->-> :
No question
#$&*
Suppose you are facing in the direction of motion. Do you perceive the component of the force along the line of motion to be forward or backward? It this component in the direction of motion or opposite to the direction of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
forward
in the direction of the motion
@&
270 degrees is 150 degrees from the direction of motion. A force which is 180 degrees from the line of motion is directly backwards relative to the motion. A force which is 90 degrees from the line of motion would be directly to the right or left, neither forward nor backward.
A force directed between 0 and 90 degrees, relative to the direction of motion, has a positive component in the direction of motion. A force between 90 degrees and 180 degrees has a hegative component in the direction of motion.
*@
#$&*
Will the object speed up, slow down or maintain a constant speed?
answer/question/discussion: ->->->->->->->->->->->-> :
Slow down some but not to a stop
@&
You are right, and this is because the force component in the direction of motion is perceived as negative, or opposed to the motion.
*@
#$&*
If you are facing in the direction of motion, then the line perpendicular to the direction of motion will run to your right and to your left. Is the component of the force perpendicular to the line of motion directed to the right or to the left?
answer/question/discussion: ->->->->->->->->->->->-> :
right
#$&*
Will the object veer to the right, to the left or maintain straight-line motion?
answer/question/discussion: ->->->->->->->->->->->-> :
right
@&
If you face forward and want to turn to the position 150 degrees counterclockwise from the forward direction, you will turn to the left, but will never get to the point where you are looking backwards.
If you wanted to turn to, say, the 230 degree position you could either turn counterclockwise, passing through the 180 degree direction then turning through another 50 degrees. Or you could turn 130 degrees clockwise.
The counterclockwise direction woud be perceived as a turn to the left. The force component perpendicular to your motion would be to the left.
*@
#$&*
Which is greater in magnitude, the component of the force along the line of motion or the component perpendicular to the line of motion?
answer/question/discussion: ->->->->->->->->->->->-> :
The force along the line of motion
@&
I agree, but there are only two possible choices and I can't tell whether this is a lucky guess or a justified conclusion. You have to show your reasoning. On a test this answer would have received no credit; as indicated in the instructions for the test all answers must be justified.
*@
#$&*
** **
5 minutes
** **
@&
Some of your answers are right and some are wrong, more or less in equal numbers, which is of course consistent with guessing.
See my notes.
Do get in the habit of explaining your reasoning. I know that's not your favorite thing to do, but it's important to develop that skill, and it helps bring everything else into perspective. Don't worry too much about whether your explanations are good or bad; just give me something to respond to.
*@