Motion of a Rolling Sphere

Relative position and motion


Part 1 Use a ruler and a piece of wood to make a ramp that is about 10 cm. above the table.  Position a small sphere at the 20 cm. mark of the ruler.  Now release the sphere and let it roll down the ramp onto a piece of white paper which is covered by carbon paper.

  1. How would you describe the tracks?
  2. What do they say about the sphere’s speed?
  3. Place an arrow beside the tracks to indicate the direction sphere is moving.

Part 2 now position the same sphere at the 10 cm. mark.  However, release it so    it rolls on a different section of the paper so the tracks can be compared.

  1. How are they similar to the first set of tracks?
  2. How are they different?
  3. How could the difference be explained?
  4. What does the distance between dots in a set of tracks say about speed?
  5. What change in the distance between dots takes place in the direction of motion?
  6. Why does this occur?

Part 3 Release a larger sphere from a distance of 20 cm.  Use another sheet of paper for this.

  1. How are these tracks different from those of the small sphere when it was dropped form the same height?
  2. How are they similar?
  3. As a sphere rolls along a table top, what factor(s) act on it to change it’s speed?
  4. What evidence do you have to support this?
  5. If this (these) factor(s) was (were) not acting, sketch how the tracks would look.

Part 4 What can you read from tracks that are a result of a collision between a sphere and a stationary object?  A piece of wood may be used as a fixed object; just slip the two papers under the wood and hold it firmly when the sphere hits it.

  1. Compare the speed of a sphere before and after colliding with a stationary object.  What happens to the speed?
  2. What evidence supports this
  3. What affect did the collision have on the direction it was moving?

Part 5 What can be read from cracks that are a result of a collision between two spheres of (a) same size (b) different size?  Place two ramps just off opposite edges of the carbon paper so they face each other.  Release a sphere from each ramp at the same time. 

  1. Compare the speed of the two spheres before and after colliding. What happens to the speed?
  2. What evidence do you have to support this?
  3. How did the collision affect the direction each sphere was going?

Part 6 Study the track below

  1. What direction is the sphere going?
  2. What evidence do you have to support this?
  3. Where did it collide with the desk leg?
  4. Compare it’s speed before and after colliding.  What can be concluded?   


Dr. Robert Sweetland's Notes ©