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Unformatted text preview: Momentum
We deﬁned an object’s momentum:
Momentum of
the object = Mass of
the object × Velocity of
the object An object’s momentum is a measure of how hard it is
to stop or change the motion of the object. How do we change an object’s momentum?
By exerting a net force on the object for some period of
time. The more force and the longer time; the greater
the change in momentum. We deﬁne an impulse exerted on an object:
Net Impulse
on object × = Net Force
on object Time force
is applied = Change in Momentum
of object and:
Net Impulse
on object 1 Momentum, Impulse, and the Second Law
(optional for 11th Grade)
The Impulse  Change in Momentum Relationship is:
Net Impulse
on object = Change in Momentum
of object = Net Force = Fnet ∆ t. Since:
Net Impulse × Time interval We can call the Change in Momentum: m ∆v
Then (setting impulse equal to change in momentum):
Fnet ∆t = m ∆v
If I solve this equation for Fnet :
Fnet = m ∆v
∆t Remember the deﬁnition of acceleration? a =
So: ∆v
∆t Fnet = m a
So this ImpulseMomentum relationship is just a
restatement of the Second Law.
2 Collisions • Elastic Collisions
Collisions that don’t generate heat or deformation • Inelastic Collisions
Collisions that do generate heat and/or deformation • Totally Inelastic collisions
Collisions in which the objects couple together. Momentum is conserved in all collisions. 3 ...
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 Spring '08
 Staff
 Physics, Mass, Momentum, net force

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