IMPULSE AND MOMENTUM I IMPULSE A baseball hits a bat The velocity of the bat changed VfVi The velocity of the ball changed VfVi Vi Vf Vi Vf B NEWTONS 3 rd Law For every action ball hitting bat there is an equal and opposite reaction bat hitting ball ID: 524872
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Slide1
Things you wanted to know, but were afraid to ask.
IMPULSE AND MOMENTUMSlide2
I. IMPULSE
A baseball hits a bat.
The velocity of the bat changed. (Vf-Vi)
The velocity of the ball changed. (Vf-Vi)
Vi
Vf
Vi
VfSlide3
B. NEWTON’S 3rd Law
For every action (ball hitting bat), there is an equal and opposite reaction (bat hitting ball).
FORCE IS THE SAME ON BOTH OBJECTS!
BUT : the velocities of the two objects are completely different.
WHY?Slide4
C. NEWTON’S 2nd LAW
He took his formula F=ma:
Changed it to F = m *(∆v/∆t)
Put ∆t on the other side to get the formula:
Affectionately called fatmav.NEWTON CALLED F∆t, ImpulseSo I = F∆t
F∆t=m∆vSlide5
II. Momentum
A Car and a bus are both going 30 m/s.
Which one has more Force?
Neither, the force on both is zeroWhich
one does more damage?The bus, but why?
V
VSlide6
B. Momentum
The bus has more of something, and it is called
momentum.
Newton named it and wrote the formula:
p = mvSlide7
III. IMPULSE MOMENTUM THEOREM
I = F∆t
p= mv
F∆t = m∆vTherefore: Impulse momentum theorem is that the impulse on an object is equal to the change in momentum of that object.
I = ∆pSlide8
IV. Law of conservation of Momentum
We are talking about collisions here!
The total momentum of all the objects before a collision must equal the total momentum of the objects after the collision.
Assuming no energy lost (elastic collision)
Reality (inelastic collision)
Pbefore = PafterSlide9
EXAMPLE
A rifle with a mass of 5 kg fires a bullet with mass of 3 g at a velocity of 700 m/s. What is the recoil velocity of the rifle?
m
1
v1 = m2v2