8th Grade Physical Science
- Unbalanced forces cause changes in velocity. As a basis for
understanding this concept:
- Students know a force has both
direction and magnitude.
- Students know when an object is
subject to two or more forces at once, the result is the cumulative effect
of all the forces.
- Students know when the forces on an
object are balanced, the motion of the object does not change.
- Students know how to identify
separately the two or more forces that are acting on a single static
object, including gravity, elastic forces due to tension or compression
in matter, and friction.
- Students know that when the forces on
an object are unbalanced, the object will change its velocity (that is,
it will speed up, slow down, or change direction).
- Students know the greater the mass of
an object, the more force is needed to achieve the same rate of change in
- Students know the role of gravity in
forming and maintaining the shapes of planets, stars, and the solar
Prior knowledge & experience:
How can you move the ping pong ball from one cup to the other without touching the cups or the ball?
How did you get the ping pong ball to move?
What caused the ball to move?
you can move the ball from cup to cup by blowing into the cup at a slight angle. The ball moves because of Bernoulli's principle. The faster a fluid moves over a surface, the less pressure it exerts. So when you blow into the cup, the air moves faster and then the pressure pushing down on the ping pong ball decreases and the ping pong ball will rise out of the cup where it can then be blown into the next cup.
When you blow on something it will push down or move away from the force.
Photographs and Movies
Wikipedia: Bernoulli's Principle