Transcript Momentum & Impulse PPT

Momentum & Impulse
Momentum & Impulse
• Words used in everyday life.
• A football team or a politician running for office
is said to have momentum.
• If you have the urge to do something, your
impulsive.
• In physics they have a slightly different meaning.
Impulse
• Impulse = the product of a force exerted on an
object and the time interval over which the force
acts.
Impulse = FΔt
Units = N·s
Momentum
• Momentum = the product of the mass and the
velocity of an object (p).
p = mv
Units = kg·m/s
• Momentum increases when mass OR velocity
increases.
??? Can a bullet and an airplane have the same
amount of momentum???
Impulse – Momentum Theorem
• If you want to know how a force that acts on an
object effects its momentum…combine the two
ideas.
Impulse – Momentum Theorem
FΔt = mΔv
Or
FΔt = pf – pi
Impulse – Momentum Theorem (cont.)
• Used to show the transfer of force between
objects.
• Ex #1 = Golf ball hit against steel wall (approx.
75 mph)
Impulse – Momentum Theorem (cont.)
• Ex #2 = Golf ball hit against steel wall (approx.
150 mph)
Impulse – Momentum Theorem (cont.)
• I – M Theorem can be used to save your life.
• How???
• A large change in momentum occurs when there
is a large impulse.
• A large impulse occurs from:
1. a small force acting over a long period
2. a large force acting over a short period
Impulse – Momentum Theorem (cont.)
• What happens when you slowly squeeze a
balloon?
• A small force is applied, but due to the length of
time, the balloon will pop!!!
Impulse – Momentum Theorem (cont.)
• What happens in a car crash?
• A large force that acts on the object for a short
period of time
Impulse – Momentum Theorem (cont.)
• An air bag actually increases the time you are in
contact with the object (steering column) and
therefore decreasing the impulse force (by giving
it time to distribute).