Fast and Easy Science Fair Projects: The Mighty Mo
Momentum: A product of force times mass
Purpose: Can momentum be increased by increasing the mass of the moving object or by increasing its speed?
Overview: Momentum is the force with which an object is moving. Objects in motion tend to stay in motion. When you start a ball rolling, it keeps rolling until friction with the surface on which it is rolling and air resistance slows it down. Momentum is a factor of mass and velocity. Mass is a measure of how much "stuff" an object is made of and velocity is how fast an object is moving and in what direction. If either the mass or the velocity is increased, the momentum will be increased, and the moving object will have more force.
Hypothesis: Two hypotheses can be stated for this experiment. As the speed of an object increases (speed is affected by the drop point being raised), the momentum increases (as measured by the depth of the hole in soft material). As the mass (weight) of an object increases, the momentum increases.
- piece of cardboard, 1 foot (30 cm) square
- ping pong ball
- golf ball
- eye dropper
Procedure: We can measure the momentum of the falling ball by dropping it into soft dough. Make a batch of dough by mixing salt, and flour. The dough must be thick enough to keep a golf ball from going through a 2-inch-thick (5 cm) batch of it when dropped from a height of about 4 feet (120 cm), but soft enough so that a ping pong ball can be dropped from the same height will make a impression.
Cut a piece of cardboard about a foot (30 cm) square. Cover the cardboard with the layer of dough.
Drop a golf ball into the dough from a height of 12 inches (30 cm). The impact will make a depression in the dough. Now hold the golf ball in your hand and raise your arm as high as you can. Drop the ball into another spot in the dough.
Compare the two depressions. Did the ball have more momentum and more force when it was moving faster? Measure the volume of each depression by using an eye dropper to fill each depression with water.
Count the number of drops each depression takes to fill it. Count the number of drops each depression takes to fill it.
In the above experiment, the mass was kept as Constant, but the velocity was increased (the Variable). Now let's keep the velocity Constant and increase the mass (the Variable).
Hold the ping pong ball in your hand and raise your arm as high as you can. Drop the ball into a clear spot in the dough. A ping pong ball and a golf ball are about the same size, but the golf ball has more mass. They were both dropped from the same height , so they were travelling at the same velocity when they hit the dough. Did the ball with more mass have greater momentum and hit the dough with greater force?
Results and Conclusion: Write down the results of your experiment. Come to a conclusion about the two hypotheses.
Something more: If you have two different velocities (by dropping two balls, each from a different height), can you adjust the mass of one of the balls to make the momentum equal? A small hole can be cut into a ping pong ball to allow different quantities of water added to it, making it heavier (increasing it's mass).
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