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Momentum and Newton’s 2nd
Law of Motion
Momentum
 Momentum - an object’s tendency
to keep moving
 Determines how difficult it is to stop
the object’s motion
 Formula:
Momentum = Mass x Velocity
Momentum
 A 1.5-kg ball is
thrown at 10
m/s2. What is
the ball’s
momentum?
 Momentum =
mass x velocity
 Momentum =
1.5-kg x 10m/s2
 Force =
15 kg-m/s2 or
15 N
Momentum
 Example:
A 100-kg fullback runs up the
middle of the football field.
He collides with a 75-kg
defensive back running
toward him. The more
massive fullback is thrown
back two meters. Although he
has less mass, the defensive
back has more momentum
because he is moving faster
than the fullback.
Momentum
 Law of
Conservation of
Momentum - the
total momentum of
any group of objects
remains the same,
unless outside forces
act on the objects.
Newton’s Second Law
 An object’s acceleration depends
on its mass and on the net force
acting on it.
 Formula:
Net Force = Mass x Acceleration
or
F = ma
Newton’s Second Law
 How much
force is needed
to accelerate a
1,700 kg car
2 m/s2?
 Force =
mass x acceleration
 Force =
1700kg x 2m/s2
 Force =
3,400 kg-m/s2 or
3,400N
Newton’s Second Law
 An object will have
greater acceleration if a
greater force is applied
to it.
 Example: If you push a
child on a swing, the
swing begins to move.
The harder you push,
the faster the swing
accelerates.
Newton’s Second Law
 The mass of an object
also affects the
acceleration of the
object.
In other words:
 If it’s big, it’s going to
move slow
 If you push it harder it
is going to go farther
Newton’s Second Law
 http://www.nbclearn.com/nfl/cuecard/50974