Worksheet 10b: Impulse, Momentum, & Collisions II
Questions
1. What happens in an auto collision:
(a) In a collision, the total change in momentum is zero. That both cars feel about
the same change in momentum, hence if you have a bigger car, you’ll tend to
have a smaller change in velocity (since
p
=
mv
).
(b) The idea here is that regardless of whether or not there’s an airbag, the change
in momentum of your head will be the same: Δ
p
. However, by the momentum
impulse theorem: Δ
p
=
integraltext
Fdt
∼
F
Δ
t
. Airbags increase the time it takes your
head to stop (Δ
t
) hence, decreases the force your head feels as it is stopping.
2. Since you cannot change your center of mass, you must do something creative to get
to the other side. One thing you can do is throw something: the center of mass will
not change, but as the thing you throw goes one way, you will move in the opposite
direction.
3. Momentum is not conserved in this case because there is an external force acting on
the ball when it bounces: the wall. The wall exerts a normal force on the ball which
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 Fall '08
 Lanzara
 Physics, Momentum, Work, 3k, 2k, 4m, 12m

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