# Shared Flashcard Set

## Details

Chapter 4
The Laws of Motion
21
Physics
09/26/2011

Term
 what is a force
Definition
 is commonly imagined as a push or a pull on some object, perhaps rapidly, as when we hit a tennis ball with a racket
Term
 is force a vector quantity and why
Definition
 yes it is, because we can control its magnitude and control its direction
Term
 give three examples of contact forces
Definition
 pull on a spring, pull a wagon & kick a football because they result from physical contact between two objects
Term
 corresponding forces are called field forces, why
Definition
 the sun has a mass M and creates an invisible influence, and the earth has a mass m and interacts with the field of the sun   another example is electic forces that exert on each other   the known fundamental forces in nature are all field forces
Term
 list the known fundamental forces in decreasing strength
Definition
 nuclear forces between subatomic particles, electromagnetic forces between electric charges, the weak nuclear force (radio active decay), and the gravitational force between objects
Term
 Newton's first law of motion
Definition
 an object moves with a velocity that is constant in magnitude and direction unless a non-zero net force acts on it   imagine pushing a book, the magnitude of the applied force is greater than the magnitude of friction
Term
 what is the net force on an object
Definition
 the vector sum of all external forces exerted on the object
Term
 what is inertia
Definition
 this is the tendency of an object to continue in its original state of motion
Term
 what is mass
Definition
 a measure of the object's resistance to changes in its motion due to a force
Term
 if you apply a force twice as large, the acceleration doubles, what can we conclude from this statement
Definition
 the acceleration of an object is directly proportional to the net force acting on it
Term
 if the force applied to one block produces an acceleration of 2, then the acceleration drops to 1, when a second block is added, what can we conclude
Definition
 the acceleration of an object is inversely proportional to its mass
Term
 what is Newton's second law of motion
Definition
 the acceleration of an object is directly proportional to the net force acting on it, but inversely proportional to the mass of the object
Term
 how can you find accerlation
Definition
 the vector sum of all forces acting on the object divided by the mass of the object equals the acceleration
Term
 what is a newton
Definition
 this is the SI unit of force
Term
 an object can move even when no force acts on it
Definition
 true, an object in motion will stay in motion if no net force acts against it
Term
 if an object isn't moving, no external forces act on it
Definition
 false, gravity does
Term
 if a single force acts on an object, the object accelerates
Definition
 true, as long as the force has more magnitude than the magnitude exert by friction
Term
 if an object accerlerates, a force is acting on it
Definition
 true, the acceleration is directly proportional to the net force acting on it
Term
 if an object isn't accelerating, no external force is acting on it
Definition
 false, inertia is the tendancy of an object to stay in motion in the absence of force
Term
 if the net force acting on an object is in the positive x-direction, the object moves only in the positive x-direction
Definition
 false, because the net force is the summation of x,y,z
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