Momentum Notes
Sports Momentum
The sports announcer says "Going into the all-star break, the
San Diego Padres have the momentum."
The headlines declare "Chargers Gaining Momentum."
The coach pumps up his team at half-time, saying "You have
the momentum; the critical need is that you use that
momentum and bury them in this third quarter."
A team that has the momentum is on the move and is going
to take some effort to stop.
Physics Momentum
Momentum can be defined as "mass in motion.“
All objects have mass, so if an object is moving, then
it has momentum - it has its mass in motion.
Momentum = mass • velocity
In physics, the symbol for the quantity momentum is
the lower case "p". Thus, the above equation can
be rewritten as
p=m•v
Momentum Units
The units for momentum would be mass units times
velocity units.
The standard metric unit of momentum is the kg•m/s.
Momentum Vectors
Momentum is a vector quantity, which is fully
described by both magnitude and direction.
The direction of the momentum vector is the
same as the direction of the velocity of the ball.
Practice
Determine the Momentum of
a. 60-kg halfback moving eastward at 9 m/s.
p = m*v = 60 kg*9 m/s
p = 540 kg•m/s, east
b. 1000-kg car moving northward at 20 m/s.
p = m*v = 1000 kg*20 m/s
p = 20 000 kg•m/s, north
c. 40-kg freshman moving southward at 2 m/s
p = m*v = 40 kg*2 m/s
p = 80 kg•m/s, south
More Practice
A car possesses 20,000 units of momentum.
What would be the car's new momentum if ...
a. its velocity were doubled.
b. its velocity were tripled.
c. its mass were doubled (by adding more
passengers and a greater load)
d. both its velocity were doubled and its mass
were doubled.
Answers
a. p = 40,000 units (doubling the velocity will double
the momentum)
b. p = 60,000 units (tripling the velocity will triple the
momentum)
c. p = 40,000 units (doubling the mass will double the
momentum)
d. p = 80,000 units (doubling the velocity will double
the momentum and doubling the mass will also
double the momentum; the combined result is that
the momentum is doubled twice -quadrupled)