1. Chapter 2 – sections 1, 2, and 3 vocabulary 1.Force – a push or a pull exerted on an object 2.Unbalance force – a nonzero net force, which changes an object’s motion 3.Balanced force – equal forces acting on an object in opposite directions 4.Net force – the overall force on an object when all the individual forces acting on an object are added together 5.Inertia – the tendency of an object to resist any change in its motion 6.Mass – the amount of matter in an object 7.Newton – a unit of measure that equals the force required to accelerate one kilogram of mass 1 meter per second per second 8.Acceleration – the rate at which velocity changes 9.Friction – the force that one surface exerts on another when the two rub together 10.Sliding friction – friction that occurs when one solid surface slides over another

2. Chapter 2 – sections 1, 2, and 3 vocabulary 11.Rolling friction – friction that occurs when an object rolls over a surface 12.Fluid friction – friction that occurs as an object moves through a fluid 13.Gravity – the force that pulls objects toward each other 14.Free fall – the motion of a falling object when the only force acting on it is gravity 15.Projectile – an object that is thrown 16.Air resistance – the fluid friction experienced by objects falling through the air 17.Weight – the force of gravity on an object at the surface of a planet 18.The Law of Universal Gravitation – the force of gravity acts between all objects in the universe

3. Chapter 2 – sections 1, 2, and 3 vocabulary 19.Terminal velocity – the maximum velocity a falling object can achieve 20.Action force – the first force exerted on an object 21.Reaction force – the force exerted back on the first object 22.Momentum – the product of an object’s mass and velocity 23.The Law of Conservation of Momentum – the rule that the total momentum of objects in an interaction does not change. 24. Potential energy – energy that is stored and held in readiness. 25. Kinetic energy – energy that an object has due to its motion. 26. Centripetal force – a force that causes an object to move in a circle. 27. Satellite – any object that travels around another object in space.