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Rolling a can down a ramp onto a rough surface.

Students keep exploring gravity and friction with a little help from bubble wrap or other rough materials.

Slippery slopes and rough roads [PDF, 279 KB]

How to use this activity

This is a hands-on exploratory activity which involves the students rolling a can down a ramp and onto a variety of surfaces.

Discussion about keeping the height of the ramp and the launch point of the can the same each time will assist students to understand the need for a consistent method if their results are to have meaning or be compared to another group's results.

At some stage, introducing the terms “variables” (in this case the surface being rolled on) and “constants” (in this case the can, the ramp height and the launch position) may be appropriate.

Depending on the ages of the students, recording of results can be done in a variety of ways. Very young children may use a visual measurement laid out on the floor to record where the can rolled to on each surface. Older children may use a form of measurement - perhaps a ruler or measuring tape or even create and use their own measuring system (e.g. their own feet or hands).

This activity is adapted from Building Science Concepts Book 42: Marbles. Additional content support for teachers can be found in this book.

Book 42: Marbles: Exploring Motion and Forces (TKI - Science online)(external link)

Where it fits in the New Zealand Curriculum

Nature of science strand

Investigating in Science – ask questions, find evidence, explore simple models and carry out appropriate investigations to develop simple explanations (Level 3-4).

  • Science activities can be used to develop any of the Nature of Science sub strands.
  • Identify aspects of Investigating in Science that your students need to get better at or understand more fully.
  • Then frame your unit to be very clear about these things when you do them.

NZ Curriculum | Science achievement objectives(external link)

Capability focus

Gather and interpret data, use evidence.

The five science capabilities (TKI - Science online)(external link)

Contextual strand

Physical World. Explore, describe and represent patterns and trends for everyday examples of physical phenomena, such as movement, forces (Levels 3-4).

Big science idea

Gravity is a force which acts to pull objects.

Friction is a force between objects when they move over one another. It can be both useful and a problem.


  • Gravity is a force pulling objects toward the Earth.
  • The amount of friction which an object encounters will affect its speed and the distance it travels.
  • The less friction there is, the further an object will travel.

Capability concepts

  • It is important to keep some things the same (constants) so that we can reliably test what we are measuring (variables). 
  • Measurements are needed to describe our observations accurately.
  • There are similarities and differences in what we observe.
    For example, in this experiment, if the angle of the ramp is changed, a reliable result about the effect of the surfaces will not be possible.

Possible learning objectives

The students can...

  • identify the things which need to be kept the same in their experimental trials (constants) and what they are going to change (variables)
  • use accurate measurements to make detailed observations
  • identify and describe patterns involving similarities and differences (order results from those with the least friction to those with the most, based on evidence)
  • compare trial results with other groups of students. Where there are differences, students can make statements/inferences about the reason for any differences
  • link gravity in this investigation to another experience of gravity they have had
  • describe what friction is in relation to their investigation and/or everyday life
  • make a statement about how friction effects distance travelled and speed.
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