#$&*
Phy 121
Your 'cq_1_22.2' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** CQ_1_22.2_labelMessages **
A 70 gram ball rolls off the edge of a table and falls freely to the floor 122 cm below. While in free fall it moves 40 cm in the horizontal direction. At the instant it leaves the edge it is moving only in the horizontal direction. In the vertical direction, at this instant it is moving neither up nor down so its vertical velocity is zero. For the interval of free fall:
• What are its final velocity in the vertical direction and its average velocity in the horizontal direction?
answer/question/discussion: ->->->->->->->->->->->-> :
a=9.8m/s^2
ds=1.22m
v0=0m/s
vf^2=v0^2+2*a *’ds
= 0+2(9.8m/s^2)(1.22m)
vf^2= 2.4m/s
@&
That would be 24 m^2 / s^2.
As to the units, it should be clear that when you multiply m/s^2 by m you don't end up with m/s.
*@
vf= 1.5m/s
ave vel=(1.5m/s + 0m/s)/2 = .75m/s
.75m/s = 1.22m/‘dt
‘dt = 1.22m/.75m/s = 1.62 s
Horizontal Ave Vel= ‘ds/‘dt
0.40m/1.62s=
=0.2 m/s
@&
You had an arithmetic error in one step; otherwise your solution is good, following all the right steps. However, due to the arithmetic error your answers are off.
*@
#$&*
• Assuming zero acceleration in the horizontal direction, what are the vertical and horizontal components of its velocity the instant before striking the floor?
answer/question/discussion: ->->->->->->->->->->->-> :
????I do not understand this at all???? Therefore the rest are confusing me as well could you explain?
@&
How fast is the ball moving in the horizontal direction just before it hits the floor?
How fast is the ball moving at this instant in the vertical direction?
Your previous solution included these quantities (though the arithmetic error had an effect on your results).
The ball's velocity at this instant is a vector, which is the resultant of the vertical and horizontal velocities.
*@
#$&*
• What are its speed and direction of motion at this instant?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
• What is its kinetic energy at this instant?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
• What was its kinetic energy as it left the tabletop?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
• What is the change in its gravitational potential energy from the tabletop to the floor?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
• How are the the initial KE, the final KE and the change in PE related?
answer/question/discussion: ->->->->->->->->->->->-> :
I think that the initial KE , the final KE and the change in PE are all related in the fact that PE and KE should be equal to one another.
#$&*
• How much of the final KE is in the horizontal direction and how much in the vertical?
answer/question/discussion: ->->->->->->->->->->->-> :
#$&*
** **
25 min
** **
I was very confused on this assignment
@&
Check my notes and see if you can correct your results for the first part, which should be easy.
Then see my note on the second part and see what you can do.
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
*@