Two trains set off at the same time from each end of a single
straight railway line. A very fast bee starts off in front of the
first train and flies continuously back and forth between the two
trains. How far does Sidney fly before he is squashed between the
A security camera, taking pictures each half a second, films a
cyclist going by. In the film, the cyclist appears to go forward
while the wheels appear to go backwards. Why?
Speeding Up, Slowing Down
Age 11 to 14 Challenge Level:
Take a look at the interactivity below which shows regular polygons
"rolling" along the horizontal surface. It leaves a trace of the
path of the red dot and on the graph it records the speed of the
Experiment by positioning the red dot at the centre of the
polygons, at one of the vertices or at the centre of one of the
sides of the polygons and explore how this affects the speed / time
Can you now work out what produced the following speed / time
The rolling polygon had a radius of 30.
Can you work out how many sides it had and where the red dot was
Try to explain how you worked it out.
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice.