Gravity is a force that pulls objects toward the center of the larger mass (which is always Earth since we are always on this planet). All matter (anything that has mass and takes up space) has gravity though- a pencil, a piece of bread, a paper clip...... We just don't feel the effects of gravity on these smaller objects around us (and our own gravitational pull) because the Earth's pull is SO much stronger than everything else.
In our lab on changing a marble's speed, we learned that gravity is one of the forces acting on the marble, which is why it rolled down our ruler ramps when we released it for each of our trials. We also learned that friction was another force acting on the marble, which helped the marble slow down and eventually come to a complete stop after it rolled down the ramp and across the floor.
In addition to learning about gravity and friction, we talked about unbalanced forces in this lab. Forces were UNBALANCED while the marble was rolling down the ramp and across the floor. Any time there is movement with an object, forces are not balanced.
In this Tug of War example, forces are NOT balanced. The group on the left is pulling with more force than the group on the right (the group is moving in the direction of the greater force).When forces are BALANCED, on the other hand, there is NO movement. We can also say "The NET force is ZERO". Forces are ALWAYS acting on objects (gravity is one that we can never escape here on Earth), but when all are "balanced", there is no movement and the net force is zero. The computer in front of you has a net force of zero- the table (desk) is pushing up on the computer with a force equal to the force of gravity pulling the computer down toward the center of Earth. (Thank goodness, right?) :-)
In this Tug of War example, if both groups of people are pulling in opposite directions with the same amount of force, the rope will NOT move.
We also learned that if two force are working together in the same direction, we add them together. Person 1 + person 2 + person 3 (all on the left) are working together to pull back to the left. If we add their individual pulling forces together, we would get their combined total force.
If two forces are working in opposite directions (against each other), we subtract them. If we could measure the force that the left group is using to pull the rope in their direction and that the right group is using to pull the ropes in the opposite direction, we could subtract those forces to find the NET FORCE (like the "net change" we learned to find in 3rd Grade).
For Behavior Bucks, leave a comment offering two new examples- one for BALANCED forces and one for UNBALANCED forces.
Mrs. Phillips :-)
5 comments:
when two dogs pull on a chew toy with the same force,the forces are balanced.
-amber W
when 2 dogs pull on a chew toy, and 1 dog is pulling with a greater force, the chew toy will go torwards the dog with the greater force.
- amber W
When you play tug of war, the stronger team will have a greater force. The other (less force) team will go towards your stronger team and lose.
When you play tug of war and the teams are exactly the same in strentgh no one moves and no team wins.
If two people are fighting over a toy the greater force will get the toy, but if they have balanced forces the toy won't move.
Preston
balanced:two mice fighting over cheese
unbalanced:one human & one mouse fighting over cheese
When two lions are both pulling on a piece of meat with the same amount of force,the two forces are balanced. When one lion starts pulling with less force the meat will go to the lion who has a greater amount of force.The forces are unbalanced.
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