F = m a

In the presence of a NET FORCE, an object experiences an ACCELERATION>> directly proportional to the NET FORCE>> inversely proportional to the MASS of the object.

Remember, though,

>> F is the NET force>> m is the mass which that net force acts on.

We often turn this around and write it as

F is the NET force acting on an objectandm is the mass of the object which the force F acts upon.

What are the

UNITSof force in

F = m a A force of ONE unit will give an object of 1.0 kg mass

an acceleration of 1.0 m/s/s ;

this force is known as

ONE NEWTON (1.0 N) .

1 N = ( 1 kg ) ( 1 m/s/s )

F = m a >> Force will be measured in newtons >> A force of 1 N will give

a mass of 1 kg

an accelertion of 1 m/s/s.

12 N = ( 3 kg ) ( 4 m/s/s ) A force of 12 N could give a mass of 3 kg

an accelertion of 4 m/s/s

12 N = ( 2 kg ) ( 6 m/s/s ) A force of 12 N could give a mass of 2 kg

an accelertion of 6 m/s/s .

We have already seen that all objects fall with the same acceleration, 9.8 m/s/s (which we approximate as nearly 10 m/s/s).

We call this

free fall.When such objects fall, the only force acting on them is their

weight, theforce of gravity.The only force on a body in freefall is the force of gravity. We call this its

weight.Since it accelerates at 9.8 m/s/s,

that

weightmust bew = (mass )x (9.8 m/s/s),

w = m g

The

weightof an object is theforce of gravityon that object.

Weight, since it is aforce, will be measured in units ofnewtons(N).

Masswill be measured inkilograms(kg).

If an object is inequilibrium--at rest--then, the net force on the object must be zero.

That is, the sum of all the forces on an object is zero when the object is in

equilibrium.

(C) 2003, Doug Davis; all rights reserved