# F(16-1) How do forces affect us?

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F(16-1) How do forces affect us?
Vocabulary Velocity Force Acceleration inertia

Describing Motion All motion is the same in certain ways. All motion is change in position. You can tell that something has moved if it’s position changes relative to something else. A stationary object or a group of objects used to determine a position change is called a frame of reference. A frame of reference is a point of view. It can change depending on the viewer.

Describing Motion Speed is the distance something moves in a certain period of time. Speed = distance /time (km/hr). Speed tells how fast or slow an object’s motion is, but it doesn’t tell you the direction of motion.

Describing Motion When you state the direction of a moving object as well as its speed, you’re stating its velocity. Velocity = speed with direction. An object’s velocity changes when there’s a change in its speed, its direction, or both. Scientists use arrows to represent velocity. The length of the arrow represents the speed measurement. The direction it points represents the direction measurement.

What forces do A force is just a push or pull. Gravity and magnetism are forces. Forces act on objects. They slow things down, speed them up, stop them, start them and turn them. Forces can change the object’s velocity.

What forces do Change of velocity is called acceleration. Acceleration is an object’s change in velocity divided by the time it takes for that change to occur.

What forces do Isaac Newton ( ) is considered one of the greatest of all scientists. One of his laws states that the greater the force on an object, the greater its acceleration. This law also says that if two objects are acted on by the same force, the object with less mass accelerates more.

Inertia An object won’t change its motion unless a force acts on it. This tendency of matter to resist a change in its state of motion is called inertia. The law of motion (law of inertia): An object at rest stays at rest, and an object in motion stays in motion at a constant velocity, unless an object is acted on by an outside force. This means; an object will not accelerate unless a force acting on it.

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