Answers

1.3 Turning and heading

Driving · Robot club · about 15 min

What this lesson is about

turn_left() and turn_right() by an angle, heading() as a compass, and turning on the spot.

• turn_left and turn_right
• Which way is which
• A square, with turns
• Turning without stopping
• Other shapes

Questions 7 marks in all

1. [1 mark]Which way does turn_right(30, angle=90) turn the robot, seen from above?

   1. AClockwise, the way a clock's hands go
   2. BAnticlockwise
   3. CIt slides right without turning
   4. DIt depends on which way the robot is facing
   Answer: A. turn_right is always clockwise and turn_left always anticlockwise, whichever way the robot faces.

2. [1 mark]The robot starts at heading 0 and runs turn_left(30, angle=90). What does heading() say? Give a whole number of degrees.

   Answer: 270 (accept within 1). Headings go 0 to 360 clockwise. A quarter turn anticlockwise from 0 is the same direction as 270.

3. [1 mark]From heading 0 the robot turns right 90, right 90 again, then left 45. What does heading() say? Give a whole number of degrees.

   Answer: 135 (accept within 1). 90 plus 90 is 180, and turning left takes 45 off, leaving 135.

4. [1 mark]What does turn_right(40) do, with no angle?

   1. AStarts turning clockwise and keeps turning until the next command
   2. BTurns 40 degrees and stops
   3. CTurns a quarter turn at speed 40
   4. DNothing, because it needs an angle
   Answer: A. Without an angle it is like forward(speed): it starts and returns at once. Use it when you want to turn until something happens.

5. [1 mark]A pentagon has five equal sides. What angle should each turn_right be? Give a whole number of degrees.

   Answer: 72. Any regular shape turns 360 divided by the number of sides at each corner, and 360 divided by 5 is 72.

6. [1 mark]Put these lines in order to drive a square: each time, drive a side, then turn.

   Number the lines 1 to 6 to put them in the right order.

   1. for side in range(4):
   2. turn_right(30, angle=90)
   3. from bugbot import *
   4. connect()
   5. forward(60, distance=25)
   6. print("home?", position())
   Answer:

   from bugbot import *
   connect()
   for side in range(4):
       forward(60, distance=25)
       turn_right(30, angle=90)
   print("home?", position())

   The drive and the turn are both indented, so both repeat four times. The print is not indented, so it runs once at the end.

7. [1 mark]After driving a square, the robot is a little away from its start and a few degrees off. Why?

   1. AThe small errors in each move add up
   2. Brange(4) only does three sides
   3. Cturn_right cannot do exactly 90
   4. Dposition() is reset at each corner
   Answer: A. Each drive and each turn is nearly right. Eight nearly right moves in a row can end up noticeably off.

The task: face east

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

# turn 45 degrees clockwise, then stop
turn_right(30, angle=45)
print("facing:", heading())

from bugbot import *
connect()
turn_right(30, angle=90)
print('facing:', heading())