Lesson 6 · Differential Drive & Motor Control — Knowledge ChecksAnswer key

Your robot is supposed to drive straight but keeps drifting to the left. What does that tell you about the two sides?

1. A.Both sides are running at exactly the same speed
2. B.The right side is running slightly faster than the left✓
3. C.The motors are running in opposite directions
4. D.One side is completely stopped

Drifting is Case 2 in miniature: the faster side travels farther, so the robot curves toward the slower one. Drifting left means the right side is winning.

You run Set effort with left 0.5 and right 0.5. What does the robot do?

1. A.Curves to the left
2. B.Drives straight forward✓
3. C.Spins in place
4. D.Stays still

Equal effort on both wheels means both sides move at the same speed — the robot goes straight.

What happens with left 0.5 and right -0.5 (one wheel forward, one backward)?

1. A.Drives straight
2. B.Spins in place✓
3. C.Drives backward
4. D.Curves gently

Opposite efforts push the two sides in opposite directions, so the robot rotates on the spot.

You set both motors to effort 0.5 and drive across a smooth floor, then across a thick carpet. What happens?

1. A.The robot travels at the same speed on both — effort sets the speed
2. B.It is slower on the carpet: effort is how hard the motors try, and the carpet fights back✓
3. C.It goes faster on the carpet
4. D.The robot refuses to move on carpet

Effort is the input (roughly, motor voltage), not the outcome. The same effort against more resistance gives less speed — exactly like pedalling a bike uphill.

A robot is asked to hold a steady speed as it drives up and over a hill. What does its effort do?

1. A.Stays at one fixed value the whole way
2. B.Rises going uphill and drops going downhill, to keep the speed the same✓
3. C.Drops going uphill
4. D.Goes to zero at the top

That's the trade: commanding speed means the robot changes effort by itself to maintain what you asked for. Commanding effort means you fix the effort and let the speed vary.

What's the difference between what Straight does and what Set effort does?

1. A.Straight drives its distance and then stops the motors; Set effort starts the motors and leaves them running✓
2. B.They do the same thing — Set effort is just the Python version
3. C.Straight leaves the motors running; Set effort stops them when it finishes
4. D.Set effort can only drive backward

Straight and Turn finish a job and stop. Set effort just sets the motors going — deciding when they stop is now your problem.

Why is 'Set effort 0.5, Sleep 3 seconds' a poor way to travel a set distance?

1. A.Sleep blocks are slower than Straight blocks
2. B.Effort is not speed — the same 3 seconds covers different distances depending on battery, surface, and load✓
3. C.Sleep stops the motors, so the robot never gets anywhere
4. D.The robot cannot run Set effort and Sleep in the same program

Timed driving is guesswork: a fresh battery on a smooth floor goes much farther in 3 seconds than a tired one on carpet. Use Straight when you want a distance, and a sensor when you want the robot to stop at something.

When is the Arcade block a better choice than Set effort?

1. A.When you need smooth, intuitive steering like a game controller✓
2. B.When you need to control each wheel to an exact effort
3. C.When you want precise, measured distances
4. D.Arcade and Set effort are exactly the same

Arcade is easiest for smooth curves and navigation; Set effort gives finer, per-wheel control when you need it.