Mr. McMartin Beta Pod Science What is Force? Mr. McMartin Beta Pod Science

Interesting Fact Basic Forces of Nature Scientists have found evidence that the interactions of only four basic forces can describe all physical properties and relationships in nature. These forces are: The gravitational force, which acts on all matter (which has mass) and on light (which has no mass). The electromagnetic force, which is responsible for the attraction and repulsion of all kinds of matter that have electric or magnetic properties. The strong nuclear force, which binds the protons and neutrons of atoms together in the nucleus. The weak nuclear force, which describes some interactions between subatomic particles.

Force and Measurement Force: a push or a pull A force can change acceleration of an object. Acceleration can be change in speed or direction Anytime you see a change in motion of an object you can be sure it was created by a force. Force is expressed (or labeled) in units called Newtons. Newton: the SI unit for force. What is force? If you notice a change in motion of an object what is it created by? What is the SI unit for force?

True statements All forces act on objects. For any push to occur, something has to receive the push. The same is true for any pull. Just because force acts on an object doesn’t mean that motion will occur. Ex. You’re sitting on a chair, but your chair doesn’t move because the floor is pushing back up on the chair. What must you have in order to apply force? T/F Any force acted on an object will make motion occur. I’m sitting on a chair and it doesn’t move. Why?

Unseen Sources and Receivers of Forces It’s not always easy to tell what is exerting a force or what is receiving a force. Ex. Magnets and Gravity Give two examples of forces that are not easy to detect.

Determining Net Force Usually, more than one force is acting on an object. Net force: the combination of all forces acting on an object. To determine the net force you must first determine the direction of the forces. Forces in the same direction: add the forces Forces in opposite directions: subtract the smaller force from the larger force. The direction would then go towards the larger force. Define Net force. There are two people moving a piano. One is pushing with 10n of force to the right and the other is pulling with 15n of force to the right. What is the net force being placed on the piano? There are two dogs playing tug of war. Dog 1 is pulling on the rope with 20 N of force to the left. Dog 2 is pulling with 12 N of force to the right. Which dog will win the battle? Include the amount of force in the winning direction.

Balanced and Unbalanced Forces If you know the net force on an object, you can determine the effect of the net force on the object’s motion. The net force tells you if the forces are balanced or unbalanced. Balanced force: When the forces on an object produce a net force of 0 N. Most forces around you are balanced. They need to be in order to stay in place. Ex. Walls around you. Unbalanced force: When the net force on an object is not 0 N. Produce change in motion Cause a non moving object to start moving Change in motion of a moving object which changes it’s direction and speed Objects can continue to move after unbalanced forces are removed. Ex. A pool ball continues to roll after being hit by the pool stick. Define Balanced force. Define unbalanced force. Give an example of a balanced force. Give one example of an unbalanced force. Name 2 of the four things unbalanced forces can do to an object.