Acceleration and Momemtum

A.  Accelerated Motion

1.  Newton's 2nd Law of Motion - Force = mass x acceleration (F = ma)

a.  Mass is in kg

b.  Acceleration is in m/s/s

c.  Force is in kg m/s/s (or N)

2.  Falling Objects

a.  All objects fall toward the earth at the same rate of acceleration.

b.  No matter what the masses may be, all objects fall at the same rate.

c.  Air resistance is the force air exerts on a moving object.

d.  Terminal velocity is the highest velocity that can be reached by a falling object.

B.  Projectile and Circular Motion

1.  Projectile motion

a.  Projectiles follow a curved path because of the earth's gravitational pull.

b.  They have two types of motion that are independent of each other:

1)  Horizontal motion (based on the initial velocity given to the object)

2)  Vertical motion (based on gravity pulling the object toward the earth)

c.  An object launched horizontally will land on the ground at the same time as an object simply dropped from the same height.

2.  Circular motion

a.  An object moving in a circular motion at the same speed is accelerating toward the center because its direction is constantly changing.

b.  Centripetal acceleration is acceleration toward the center of a curved path.

c.  Centripetal force is the force that causes a moving object to move in a curved path.

d.  Centrifugal force is actually just an imaginary force; it does not really exist.

e.  Weightlessness in orbit around the earth is obtained because objects are constantly falling toward the earth, but the objects have enough forward speed to keep them in orbit.

C.  Newton's 3rd Law of Motion

1.  Action-reaction

a.  To every action, there is an equal and opposite reaction.

b.  The pair of forces always act on different objects and are each unbalanced on the object they act upon.

c.  Rockets produce a thrust force and move the opposite direction (they do not "push" against the earth to liftoff).

2.  Momentum

a.  This is a property any moving object has due to its mass and velocity.

b.  Formula:  p = m x v

c.  Unit:  km m / s

d.  Momentum can be transferred to other objects ( p[1] = p[2] )

e.  The law of conservation of momentum - the total amount of momentum of a group of objects does not change unless outside forces act on them.