Stack of Quarters (Randy Daniels)

Author

Randy Daniels

Principle(s) Illustrated

1. Newton's 1st Law of Motion - An object in motion (or at rest) will remain in motion (or at rest) unless acted upon by an outside force.

Standards

• MS-PS2-2. Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.[Clarification Statement: Emphasis is on balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces, mass and changes in motion (Newton’s Second Law), frame of reference, and specification of units.]

• [Assessment Boundary: Assessment is limited to forces and changes in motion in one-dimension in an inertial reference frame and to change in one variable at a time. Assessment does not include the use of trigonometry.]

Questioning Script

Prior knowledge & experience:

If I strike a tower of coins with a butter knife, the tower should fall over.

Root question:

How does the tower stay up after I strike the bottom of the stack with a knife? How does only one coin come out?

Target response:

The knife strikes the coin with enough speed that the friction between the coins is overcome, allowing the coin to come free without dragging another one along with it. Inertia keeps the coins in the tower falling on top of each other.

Common Misconceptions:

The coin tower will topple over regardless of where or how I strike it.

Photographs and Movies

Put all photos in the class Picasa Album and reference here. Do not upload the photos directly to this wiki as there is not enough memory in the website.

Put all movies in your own Youtube account. Make sure that the account is set for public viewing.

References

Reference 1 -Steve Spangler Science, Coin Tower - link.