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Ice Block Sledding - Overcoming Friction

Friction and gravity are in a constant battle much of the time. Think of this: if you are standing on a grassy hill with your toes pointed downhill, it is likely that you will not go sliding down the hill even though gravity is pulling you that direction. Why don't you slide down the hill? Your shoes provide friction. The underside of the shoe interacts with the grass blade and together they provide a friction force that overcomes the work of gravity trying to pull you down. Without getting too technical there is another force called the Normal Force that is keeping you from shooting directly into the center of the Earth but that will be explained in a different experiment.

For this experiment I am going to show how we can overcome the friction force by reducing the amount of friction and allowing gravity to do its work. All I need is a big block of ice and a hill. I call this "Ice Block Sledding".

The ice is much more smooth than my shoes so it experiences less friction on the grass. Likewise, the ice melts when it experiences friction because it heats up and water reduces the friction force even further! This means that I can sit on a big block of ice, lift up my feet and let gravity and friction take me for a ride! The trail of water made by friction between the ground and the melting ice can be clearly seen in the FLIR thermal camera.

This is one experiment you need to try at home!

How to make an ice block for sledding

  • Find a box or plastic tote that will fit in your freezer.

  • Line the box or tote with a garbage bag

  • Fill the mold with water (remember that water expands when frozen so do not overfill)

  • Place ice block mold in your freezer

  • Drill a hole and thread a rope through. Tie it securely.

How to sled with an ice block

  • Set the ice block at the top of a gentle grassy slope

  • Place a towel on top of the ice

  • Sit on the towel / ice

  • Lift up your feet and hang on!

For more episodes of Invisible Labs with Craig Beals, click the logo:

Sponsored by FLIR


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