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1.3 Scr0330: sequence, selection, and loop in scratch 2.0.  (Page 9/9)

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This is the action that is required whenever either of the touching blocks is true. In other words, whenever the basketball touches either of the beachballs, it must turn to facethe opposite direction and be prepared to move 90 steps in that direction the next time the user clicks the basketball.

An online version of this program is available

A copy of this program has been posted online for your review (see Resources for the URL) . If you don't find the program using that URL, search the Scratch site for the usernamed dbal.

Run the program

I encourage you to use the information provided above to write this program. Experiment with the code, making changes, and observing the results of yourchanges. Make certain that you can explain why your changes behave as they do.

Just for fun, use blocks from the purple Sound group and add some sound effects to your program.

I also encourage you to write the program described below.

Student programming project

Write a Scratch program named IfWithVar01 that produces the output shown in Image 13 when the user clicks the green flag. (Don't be concerned about matching the values in the x and y variables in Image 13 . )

Image 13. initial output from the program named ifwithvar01.

Missing image.
Image 13. Initial output from the program named IfWithVar01.

Orthogonal axes in Cartesian coordinates

When the user clicks the green flag, a DrawingPencil sprite draws a pair of orthogonal axes that intersect at the origin in the white Stage area.Make the horizontal axis extend from -200 to 200. Make the vertical axis extend from -100 to 100.

Draw a straight line to the location of the next mouse click

Each time the user clicks the mouse in the white Stage area (after the user has clicked the green flag) , a straight line is drawn from the current location of the DrawingPencil to the location where the mouse click occurred. Image 14 shows an example output after two mouse clicks.

Image 14. program output after having clicked twice in the stage area.

Missing image
Image 14. Program output after having clicked twice in the Stage area.

A sneak peek at the solution

In case you need to sneak a peek at the solution to this programming project, acopy of this program has been posted online for your review (see Resources for the URL) . (If you don't find the program using that URL, search the Scratch website for the usernamed dbal .)

Once you locate the project on the Scratch web site, you can execute it online.

Summary

I began by explaining structured programming, the sequence structure, the selection structure, and the loop structure. Then I presented andexplained a Scratch program that illustrates the selection structure. (The sequence structure is so simple that it doesn't require an explanation. The loop structure will be explained in a future module.) The program also illustrates the handling of mouse events and Cartesian coordinates.

Finally, I provided the specifications for a student-programming project for you to write to demonstrate your understanding of what you learned from thefirst program.

Copies of both programs have been posted online for your review (see Resources for the URL) . If you don't find the program using that URL, search the Scratch site for the usernamed dbal .

What's next?

In the next module, I will teach you about arithmetic operators. In the two modules following that one, I will teach you about relational and logicaloperators and how to use those operators to write the conditional expressions used in selection and loop structures.

Resources

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Scr0330: Sequence, Selection, and Loop in Scratch 2.0.
  • File: Scr0330.htm
  • Published: 05/11/13
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freelyavailable on cnx.org and that it was made and published without my prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, Teaching beginners to code. OpenStax CNX. May 27, 2013 Download for free at http://cnx.org/content/col11498/1.20
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