Measures acceleration of a falling weight, calculating the speed of a moving cart, or aids in the study of the forces of friction. A paper strip is pulled through the timer while a spark, at a very precise interval, is created burning tiny dots into the paper strip as it passes. The faster the strip moves, the larger the distance between dots making it is easy for the student to calculate the rate of speed of acceleration. Everything on the spark timer is enclosed for safety. Instructions included.