Transcript Intro to Momentum

Linear Momentum
Physics
Mrs. Coyle
Linear Momentum, p
p= m v
• Momentum is a vector.
• The direction of momentum is the same as the
direction of the velocity of the object.
• Unit: kg m/s
or N s
• “Inertia in Motion”
Question 1:
• What has more momentum, a dump
truck at rest or a pebble moving down a
hill at 1m/s?
Question 2
• How can you change the momentum of
an object?
Impulse =
Impulse = p = m v = Ft
Problem 1
• Starting with Newton’s second
law, show that for a constant
force, p = m v = Ft .
For a given change in velocity,
p is constant :
To reduce the force of impact,
increase the time of impact.
Question 3:
• How do you have a better chance
of winning in a water balloon toss
contest?
Question 4:
• Why does a boxer “roll with the
punches”?
Question 5:
• Why should you follow through in
a serve when playing tennis, or
when hitting a baseball?
Problem 2
A ball at rest has a mass 0.5kg and
is kicked with a force of 40N. The
impact lasts 0.2s. Find:
a) The change in momentum of the
ball.
b) The final velocity of the ball.
Answer: a) 8 Ns, b)16m/s
Problem 3
• A football player of mass 130kg
travelling at 12.0m/s collides with
another player and comes to rest
in 0.90s. What was the force of
impact?
• Answer:1,733N
Impulse is the area under the
curve in a graph of F vs t.
F
t
Some Engineering Applications
Question 6
• Why are airbags used?
M
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X
P
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MARS LANDER AIR BAGS
Rover Exits the Lander
Applications in Engineering
Household Items
MILK BOTTLES
THE EGG CARTON