Transcript File - Mrs. Ward`s Science

Topic 3-1
Momentum
Momentum
AKA:
Inertia in motion
Defined:
Resistance to change based
on your mass and velocity
Examples:
Slamming on the breaks
Turning too fast
Mathematically defined:
your mass times your
velocity
p=mv
Impulse
Defined:
Force required to
change momentum
Requires Force and time to
change momentum
AKA:
Change in Momentum
Therefore:
Ft = Δ(mv)
Changing Momentum
Increasing
(ex. Hitting a golf ball)
1. Apply as much force
as long as possible
1.
2.
Force will vary from
instant to instant
Force will be given as
an average
Decreasing
(ex. slowing a car that is
about to crash)
1. The longer the time
interval, the smaller
the force of impact
Sample Questions
A golfer hits a 0.05 Kg
golf ball, giving it a
speed of 75 m/s. What
impulse does he impart
on the ball?
Wayne hits a stationary
0.12 Kg hockey puck
with a force that lasts
1.0 x 10-2 seconds and
creates a velocity of
20.0 m/s. With what
force did Wayne hit the
puck?
Special Consideration
If an object bounces; its change in momentum is
actually greater than if an object hits and sticks.
Remember negatives show directionality so the initial
velocity would be negative to show it moving the
opposite direction compared to the final velocity
(final velocity + Initial velocity)
Conservation of Momentum
Defined:
Momentum is neither created or destroyed;
only transferred from one object to another.
Mathematically:
(m1v1)I + (m2v2)I = (m1v1)F + (m2v2)F
Types of Collisions
Elastic:
Objects collide and move
separately from one
another after collision
Inelastic:
Objects collide, stick, and
move as one object
Recoil:
Objects start together and
move apart and separately
Formulas:
Same as on previous slide
(m1v1)I + (m2v2)I = (m1+m2)vF
vI(m1+m2) = (m1v1)F + (m2v2)F
Sample Problem 1
The sumo Twins have a combined mass of 200
Kg and are zooming around in a 100 Kg
bumper car at a speed of 10 m/s. They collide
into Melinda’s car, which is standing still.
Melinda has a mass of 25 Kg. After the
collision, the twins continue to move forward
at a speed of 4.12 m/s. How fast is Melinda’s
car traveling across the floor?
Sample Problem 2
Most accidents have rubber Necker's. Molly
slowed her 800 Kg sports car down to 13 m/s
to on look at a grizzly auto wreck.
Unfortunately, Bubba in his 1200 Kg truck
never slowed down from 25 m/s. What would
their combined velocity be if they locked
bumpers?
Sample Problem 3
Diver Dan, a 65 Kg spear fisherman shoots a 2
Kg spear with a velocity of 15 m/s trying to
hit a fish. He misses the fish. The recoil of
the spear gun causes Dan to move backwards
at what speed?
Special Consideration
If two objects are both initially moving and
headed in different directions; we need to treat
one of their initial momentums as a negative
value to show directionality.
Think of a car headed north at 5 m/s and a car
headed south at 5 m/s collide. One of their
initial momentums would be represented as a
negative value