Transcript Slide 1

LINEAR MOMENTUM:
A. MOMENTUM – A vector quantity defined as the product
of an object’s mass and velocity
B. FORMULA – momentum = mass x velocity
p=mxv
C. UNITS – kgm/s
D. EXAMPLES:
PROBLEM:
1.A 2250kg pickup truck has a velocity of 25m/s to the east.
What is the momentum of the truck?
2. What velocity must a car with a mass of 1210kg have in order
to have the same momentum as question #1?
3. An ostrich with a mass of 146kg is running to the right with
a velocity of 17m/s. Find the momentum of the ostrich.
4. A 21kg child is riding a 5.9kg bike with a velocity of 4.5m/s
to the northwest.
a. Find the total momentum
b. Find the momentum of the child
c. Find the momentum of the bike
IMPULSE:
A. IMPULSE – For a constant external force, the product of
the force and the time over which it acts on an object.
A change in momentum.
B. FORMULA – Force x time interval = change in momentum
F = ma = m x v/t = Dp/Dt
FDt = Dp = mvf – mvi
C. UNITS – kgm/s and always a direction.
D. EXAMPLES:
PROBLEMS:
1. A 1400kg car moving westward with a velocity of 15 m/s collides
with a utility pole and is brought to rest in 0.30s. Find the
magnitude of the force exerted on the car during the collision.
2. Find the force exerted in question one if the speed is doubled.
3. A .40kg soccer ball approaches a player horizontally with a velocity of
18m/s to the north. The player strikes the ball with a velocity of
22m/s in the opposite direction. Find the impulse on the ball.
NOTE: Extending the time interval over which a constant force is
applied allows a smaller force to cause a greater change
in momentum than would result if the force were applied
for a very short time.
Stopping times and distances depend on the
Impulse-Momentum Theorem.
1. A 2250kg car traveling to the west is slowed down uniformly from
20.0m/s to 5.00m/s in 4.00s. What constant force acted on the car
during this time? How far did the car travel during the deceleration?
2. How long would it take the car to come to a complete stop?
3. What would be the total stopping distance?
4. What if the car was 3250kg, how much force would be required to
cause the same acceleration as #1?
5. How far would the car travel before stopping?
CONCEPT CHALLENGE:
EGG DROP!!!!!!!