PART 1
‘Just
before finals you decide to visit an amusement park set up in the Metrodome.
Since it is a weekend, you invite your favorite niece along. She loves to ride
on a Ferris wheel, and there is one at the amusement park. The Ferris wheel has
seats on the rim of a circle with a radius of 25 m. The Ferris wheel rotates at
a constant speed and makes one complete revolution every 20 seconds. While you
wait, your niece who has a mass of 42 kg, rides the Ferris wheel. To kill time
you decide to calculate the total force (both magnitude and direction) on her
when she is one quarter revolution past the highest point. Because the Ferris
wheel can be run at different speeds, you also decide to make a graph which gives
the magnitude of the force on her at that point as a function of the period of
the Ferris wheel.’





Construct specific equations:
v = 2πr / T find v.
Fcos(Q) = m v^{2}/r
Fsin(Q) = mg
By using these equations find Q.
F = √[(mg)² +(mv² / r)²] find F.
Checked for sufficiency. It’s o.k.

The niece’s
velocity is; v = 2 π r / T
= 2
π 25m / 20s
=
(3,14) × (2,5) m/s = 7,85 m/s = v
= × (25 m) /
(7,85m/s)²
88,2 º
The direction of force is 88.2 º above the horizontal.
Squaring and adding
Fcos(Q) = m v^{2}/r and Fsin(Q)
= mg ;
Therefore F= 424,42 Newton
Therefore the magnitude of the force is 424,42 Newton
and 88,2 º above the horizontal.
If T increases,
v will decrease so F will also decrease.


EVALUATION
Is the answer
properly stated?
– Yes, units
are convenient because we found force’s unit as Newton and tetha’s unit as
‘degree’as we guessed.
Is the answer
reasonable?
– Yes all
values are logical because for a 42 kg object and 25 m radius of ferris wheel
the magnitude of the force as 424.42 newton is reasonable. Tetha is also in
the sama vein.
Is the answer
complete?
– Yes.

REFERENCES:
–
For
the format of problem solving strategy the worksheet given and the online
document below is used.
[Online Document]
http://serc.carleton.edu/sp/library/context_rich/problem_solving.html
–
For
the physical solution of the problem Young
& Freedman (12th edition) is used as a guide.
PART 2
Problem: After a tiring week, you want to do entertaining
activities in weekend then call your boyfriend. He suggest to play with his
remotecontrol car with mass 1.60kg which you gived to him as a birthday gift
last weekend. Then you accept the proposal.
When you play with the car you realized that it moves at a constant
speed of 12.0 m/s. Then you decide to make a metal cylinder that has a radius
of 5.00m from your boyfriend’s small fry to make the play more
entertaining. After that you put the car
in this vertical circle inside a hollow metal cylinder. Car turns in the
cylinder a lot of times then your boyfriend wonder how the car do not drop from
the top point. At that time, you decide to explain him firstly the magnitude of
the normal force exerted on the car by the walls of the cylinder at the bottom
of the vertical circle. After that you want to answer his question by finding
the magnitude of the normal force again but this time at the top of the
vertical circle. Do it! :)




Construct specific equations:
Check for
sufficiency:
Three unknowns and three equations.
Outline the math
solution:
Solve third equation then by using it solve first and
second equations.

SOLUTION:

EVALUATION
Is the answer
properly stated?
– Yes, units
are convenient because we found forces’ unit as Newton as we guessed.
Is the answer
reasonable?
– Yes all
values are logical because for a 1.60 kg object and 5.0 m radius of cylinder
the magnitude of the force as 61.8 and 30.4 newton is reasonable.
Is the answer
complete?
– Yes.

REFERENCES:
–
For
the format of problem solving strategy the worksheet given and the online
document below is used.
[Online Document]
http://serc.carleton.edu/sp/library/context_rich/problem_solving.html
–
For
the writing a context rich problem the websites below are used as a guide.
[Online Document]
http://groups.physics.umn.edu/physed/Research/CRP/crcreate.html
–
For the skeleton of the problem Young & Freedman
(12th edition) is used as a guide.
******************
ben küçükken fen lisesine gitmiştim de o günlerde bunları anlardım...hey gidi günler:(
YanıtlaSildemekki o günlerden bu yana işler pek de fazla değiğşmemiş, bu da başka bir bakıs açısı. :)
Sil