3 Must Try Inertia Challenges For The Classroom

What is Motion?

Energy is the ability to do work.  In order to do work, a force must be applied.  A force can be a push or pull that causes an object to move, stop, or change direction. A force strong enough creates motion.  Motion is the act of moving.   If there is no force there will be no movement. 

Energy can be kinetic or potential.  Kinetic energy is the energy of motion.  Potential energy is stored energy based on its' position or condition.  When you hang from the monkey bars you contain lots of potential energy.  The potential to fall.  When you let go you now have kinetic energy.  You fall to the ground. 

Exploring Newton’s Laws of Motion

The first law of motion is inertia.  All objects have inertia.  The law states that an object will stay at rest unless a force acts on it and an object will keep moving until a force stops it.  When 5 pennies are stacked on a piece of cardboard on top of a can they are at rest. The pennies are not moving and have no kinetic energy.  The pennies have the potential to move if the cardboard is pulled out from under the pennies.  

When the cardboard is pulled out from under the pennies the pennies do not move.  The force was applied to the cardboard.  The pennies then lose the support of the cardboard and fall into the can.  It takes some practice to pull the cardboard straight out without having it push on the pennies.  If that happens the pennies are not at rest and will go flying into the air.  Simply, if nothing touches the pennies they will not move.

If the pennies are at rest, why did they fall into the can?  Without the cardboard, the force of gravity

pulled the pennies into the can.  The pennies had Gravitational potential energy.  Gravity is the attraction of matter to each other.  It is an invisible, weak force.  The larger the object the more gravity it has.  When on earth, it has the largest gravitational pull. The pennies fall straight towards the earth.  This is a great trick and demonstration showing that an object only moves if a force is applied. 

That demonstration is great but let's take it up a notch!  There are some fantastic inertia challenges.  Your students will love them and be amazed by their skills.  Disclaimer: You will not have a quiet classroom when performing these challenges!

Challenge 1

Can you remove the card 
without touching the penny?

Supplies 

Penny  Notecard  Index Finger

Directions

1.Using your non-dominant hand, balance the notecard on your index finger.

2.The penny is then placed on the notecard directly above your index finger.

3.Using your dominant hand, flick the paper straight out.  The goal is to get the penny to stay on your finger.

Explanation and Tips

This can be done, but it is challenging.  It is so exciting when you get it.   You will realize that you need to move the card without affecting the penny.  The tough part is keeping your index finger steady.  Do not give up.  This demonstration proves perfectly that an object will not move unless a force is applied.  The wonders of inertia.

The more mass something has the more it will resist movement.  Stacking more pennies actually makes it easier.  Try 5 pennies and see what happens.

Challenge 2

Quarter/Dollar Challenge

Supplies

Crisp dollar or higher bill if you dare, Quarters, Glass Soda bottle.

Directions:  

1.  Place the dollar bill on top of the bottle.  It should be on the end of the bottle with the rest hanging out on the other side.

2.  Place 5-10 quarters on top of the dollar bill centered with the opening of the glass bottle.  Make sure they are lined up.

3.  With your dominant hand hold the edge of the dollar bill hanging off.  Don't pull or everything will fall off.  Be delicate.

4.  Using your other hand do a quick karate chop through the dollar bill so it slides out from under the quarters.  You are not ripping the dollar bill.  Don't use a lot of force.  Just a quick chop.

Explanation and Tips

Classic inertia at it again.  If you karate chop correctly not force is applied to the quarters.  They stay right on the bottle.  The more quarters the easier this trick is.  Can you successfully perform it with one quarter?  

This setup can be tricky for little ones.  Sometimes I will hold the bill while they karate chop.  My kindergarteners are very good at this trick.

Challenge 3

Hex Nut Trick

Supplies:  Empty soda bottle(Size does not matter.), Plastic ring or cardstock made into a ring, small hex nut that fits into the bottle.

Directions

1.  Place the bottle on a table. 

2.  Balance the plastic ring on top of the bottle.  

3.  Balance the hex nut on top of the ring so that it lines up with the opening of the bottle.  This is tricky.  Have a partner help you line them up.

4.  With a quick motion grab the ring and pull it straight back.  Do not lift it up.  It must go straight back.  

5.  If lined up correctly the hex nut will fall into the opening of the bottle.  Take a bow!

Explanation and Tips

Good old inertia has done it again.  This is a classic trick.  When the ring is pulled straight back no force is applied to the hex nut.  The ring comes out and gravity pulls the hex nut down.  

If the hex nut flies into the air you know you did not pull straight.  Kids like to tip the ring causing the hex nut to slide into the bottle.  That is not the same thing, so keep a lookout for it.

Have fun exploring Inertia. 

 

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