Notes: Motion and Forces A.What is motion? 1. An object is in motion if it involves a change in position relative to a reference point. 2. Distance is the total length of the route an object travels when it moves. a. Speed describes the change in position (distance) during a period of time, without respect to direction; Formula: speed = distance / time b. Velocity is the speed of an object and its direction of motion; describes how position changes over time (Ex. the speed of a car is 65 mph; the velocity of the car is 65 mph traveling east)

3. Acceleration describes how velocity changes over time, it can include an object’s speeding up, slowing down, and/or changing direction Formula : acceleration = (final speed – initial speed) time B. What is force? 1. A force is a push or pull on an object 2. balanced forces do not change an object’s motion 3. unbalanced forces cause the motion of an object to change 4. types of forces – magnetic, electrical, gravity, friction, buoyancy, tension C. In the late 1600’s, Sir Isaac Newton identified three basic laws of motion.

1. Newton’s First Law of Motion a. An object at rest will remain at rest and an object in motion will remain in motion unless acted upon by an unbalanced force b. Also called the law of inertia. Inertia – is the tendency of an object to resist any change in motion 1.) The amount of inertia an object has depends on its mass. Mass is the amount of matter in an object. 2.) The greater the mass of an object, the greater its inertia 2. Newton’s Second Law of Motion a. The overall force on an object is equal to the mass of an object multiplied by the acceleration of the object; Force = mass x acceleration

b. If the force on an object increases, then acceleration will increase. c. If the mass of an object increases, the acceleration will decrease. 3. Newton’s Third Law of Motion a. When one object exerts a force on another object, the second object exerts an equal but opposite force back on the first object. b. This is known as the law of action-reaction D. The Force of Gravity 1. Gravity is the force that pulls objects toward each other. 2. Weight is the force of gravity on a person or object at the surface of a planet

3. The law of universal gravitation states that the force of gravity acts on all objects in the universe. 4. The strength of gravity between two objects depends on their masses and the distance between them. a. The greater the masses of the objects, the stronger the pull of gravity. b. The greater the distance between the objects, the weaker the pull of gravity.