Begin with a class discussion about gearing down. Remind them of the Exploring Gears lesson where they discovered that gearing down results in a slower motion of the follower gear.
2. Also discuss the effects of friction and how it reduces slipping between two objects. Friction is what allows a person to walk across a floor and allows a car to travel across a road and up an incline. Explain how friction is also dependent on weight.
3. Tell the class that they will be building and programming a car to travel up a steep incline. Show them your example car and how you geared down. Also point out how you shifted the weight of the car to increase friction at the wheels.
4. Allow 10 minutes for student pairs to build their cars. Have students program their cars to accelerate from rest. This will ensure that their cars don’t slip at the base of the incline.
Below is a good program to use as an example:
When “A” is pushed, the motor will turn at a power level of 5 for 1.5
seconds and then stop.
When “D” is pushed, the display value begins at 8. The motor will turn
at a power level of 8 for 0.5 seconds. The display also subtracts 1 from 8
to display 7. For each consecutive loop, the power level will be one less
than it was in the previous loop. Thus the motor is decelerating.
When “D” is pushed, the display value begins at 1. The motor will turn
at a power level of 1 for 0.5 seconds. The display also adds 1 to 1 which
displays 2. For each consecutive loop, the power level will be one more
than it was in the previous loop. Thus the motor is accelerating.
The program will only work if the tilt sensor is in a certain orientation. If the tilt sensor is in position, the motors will turn in time with the music.
The display begins with a value of 10 (the motion sensor has a range from 0-10). The value of the motion sensor is subtracted from 10 and a message with that value is sent out. If the message equals 0, then the motion sensor is registering an open music box. This will make the LEGO person dance to the music. Otherwise, nothing will happen.
This program can be used to accelerate the car up the ramp. Starting
from rest creates enough traction to stop the car from slipping.
This program uses the motion sensor to determine the speed of the car. If
the tilt sensor is tilted upwards, the car will slow down and if the tilt
sensor is flat, the car will travel faster.