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Newton's Laws Stations Activity
Whack a Stack (student handout)
Materials:
• Five or six wood blocks
• Stick
Step-by-Step Procedure:
Caution: your blocks will go flying, so make sure nobody is standing where they might get hit!
1. Stack the blocks neatly with the large sides parallel to the tabletop, and the long sides facing you.
2. Hold the stick along the tabletop, near the stack of blocks.
3. Firmly and rapidly whack the meter stick back and forth just above the tabletop.
4. With each whack, knock another block out from the bottom of the stack.
5. Do one block at a time, swiping in the same direction each time, for safety.
Test Your Understanding:
What's Going On?
1. What happens when the bottom block is whacked out of the stack? The rest of the stack should essentially drop
straight down onto the tabletop.
2. When the bottom block is knocked away by the force of the stick, the rest of the stack resists moving horizontally
along with it. This is due to a phenomenon called inertia — a resistance to change in motion. Inertia is the subject of
Isaac Newton's first law of motion: An object remains at rest, or an object in motion stays in motion, unless acted upon
by an unbalanced force.
3. Mass is a measure of inertia, as shown in Newton's second law: Force = Mass x Acceleration. In other words, the more mas-
sive something is, the harder you have to push or pull it to change its state of motion. The stack of blocks is fairly
massive, so it has quite a bit of inertia.
4. You may notice, though, that the stack moves horizontally just a bit, especially as the stack gets smaller and therefore
has less inertia. That's because there's a frictional force between the bottom block and the stack above it. If we could turn
friction off, the stack wouldn't move sideways at all.
Use complete sentences to explain how Newton's laws are involved in this activity.
Name: Class: Date:
