# Physics- Review of Some Topics, Dec. 1, 2008

Just a quick review of some of the topics we have covered since the midterm…

Work

W= Fd

– work is defined as a transfer of mechanical energy

– it causes an object to change or move

– work is always done on an object

– is measured in N*m

– review the conditions for when work is done (work is not done hen there is no change in condition, there is uniform motion or if the force applied is perpendicular to the direction of the motion)

– Review practice problems #1-3 on page 221 and #4-10 on page 225 for a refresher

Momentum

p = mv

– the momentum an object possesses is related to the product of its mass by its velocity

– the direction of the momentum is the same as its velocity (is a vector)

– has a unit of kg*m/s

– used when dealing with non-elastic collisions- it’s easier to describe the “quantity of motion” of an object before and after a crash than to try and analyze it during the moment of

Impulse

J = F(delta)t

F(delta)t= (delta)p

F(delta)t = mv2-mv1

– is the product of the force exerted on an object and the time interval over which the force acts

– impulse is a measure of the change in momentm

– direction of impulse is the same as the direction of the F applied

– unit is in N*s

– Review problems 29 on 197, 30-32 on 200 and 33-35 on 203

For additional problems, check out: #37-42 on page 209 and #15, 17, 20, 23-28 on page 275 and 276.