Are you walking in a winter wonderland? Instead of getting snowed in, get snowed out!
See what the white fluffy stuff can teach about Newton's Laws of Motion with sledding. Thirsty for more? Do our hot chocolate solvent activity and enjoy a tasty (and toasty) chemical reaction.
Take your sled(s) to the slopes. Start at the top of the hill and ride one of your sleds down. When you come to a complete stop at the bottom, mark the spot by digging a line in the snow with the heel of your boot, or determine another durable method to mark the spot. Repeat the process with another sled and a third if you have it. Which goes the farthest? Why do you think that is? Now make a line near the bottom of the hill but a little way up from the where your sleds came to a stop. Have your adult supervisor near it with the stopwatch. Go down on each sled in turn and time how long it takes to cross the line. Which sled goes fastest? Why do you think that is? Finally, why doesn't the sled slow to a stop at the bottom of the hill? What happens if you add weight to your sleds, like another rider; does that make your sled go faster or farther? Is there any difference in times if you go down face first, rather than feet first? Why would that be? Make predictions about which sled set-up will produce the fastest run time and which will produce the longest run time. Record your results.
If you're more of a daredevil, try making a jump by building up mounds of snow near the bottom of the run. Try building one gently sloping mound and another that's steeper and higher. Does one launch the sled higher or farther than the other? How about speed? Does one of the jumps produce faster run times than the other? Record your results.
To understand sledding better, we need to spend some time with Sir Isaac Newton and his laws of motion. Newton's First Law of Motion, the Law of Inertia, states that an object's velocity (or speed in a given direction) will not change unless it is acted on by an outside force. This means that an object at rest will stay at rest until a force causes it to move. Likewise, an object in motion will stay in motion until a force (push or pull) acts on it and causes its velocity to change.
The greater mass or velocity an object has, the greater its inertia. For example, it takes a pretty strong push to get you and a friend on the same sled moving, but once you gather speed you'll keep going even at the bottom of the hill where the run flattens out. It takes much more force to stop you and your friend on the sled than to stop an empty sled (one with less mass).
Newton's Second Law of Motion states that "when an object is acted on by an outside force, the strength of the force equals the mass of the object times the resulting acceleration." In other words, the formula to use in calculating force is force=mass x acceleration. Opposing forces, such as friction, can be added or subtracted from the total to find the amount of force that was really used in a situation.
Perhaps the most familiar, Newton's Third Law of Motion says that "for every action, there is an equal and opposite reaction." Use a pair of roller skates and a ball to show how this works. What happens when you're standing still in skates and then throw a ball hard? The force of throwing the ball (action) pushes you and your skates in the other direction (reaction).
But with sledding there's a little more to consider: like gravity and normal and frictional force. Gravity refers to the attraction between any two objects that have mass and occupy space. It's what keeps us anchored to the earth and what pulls a ball down after it's tossed into the air. Friction is the resistance to movement between two objects that are in contact with one another. There is usually less friction between smooth surfaces than rough ones.
Normal force is caused by two bodies in direct contact and is perpendicular to the plane of contact. So when you sit on your sled, gravity pulls you toward the hill and normal force acts in the opposite direction. Since the hill is not horizontal, the slope of the hill acts with the gravitational force, propelling you down the hill. Frictional force exists between your sled and the snow and is directed back up the hill. That's why you'll eventually stop at the bottom of the hill and why certain sleds allow you to go faster than others.
For deeper study into frictional force and the coefficient of friction, go here.
These kids are are total lugers! Watch the video to learn more.
Check out sledding hills around the nation and submit your favorite!
Sled safely with these safety tips.
Luge is the French word for sled.
Sleds existed as early as AD 800.