Unformatted text preview: annot be an
elastic collision
C) we don't know the mass of both blocks, so we can't tell if energy or
momentum are conserved Physics 211 Lecture 13, Slide 10
Physics Forces during Collisions
Forces dP
Ftot dt Ftot ma Ftotdt Pt2 Pt1 t2 Ftot dt dP t1 Fave t F P P Fave t Fave Ftotdt Favet t2 t t
ti tf t1 Impulse P Fave t Act Two identical blocks, A and B, initially are moving on
frictionless air tracks. The initial speed of block A is twice
as that of block B. You now apply the same constant force to
both blocks for exactly one second.
F
air track A 2v F
air track B v The change in momentum of block A is:
A) Twice the change in momentum of block B
B) The same as the change in momentum of block B
C) Zero.
D) Half the change in momentum of block B
Physics 211 Lecture 13, Slide 12
Physics P Fave t Act Two boxes, one having twice the mass of the other, are
initially at rest on a horizontal frictionless surface. A
force F acts on the lighter box and a force 2F acts on the
heavier box. Both forces act for exactly one second.
Which box ends up with the biggest momentum?
A) Bigger box F B) Smaller box M 2F C) same 2M Physics 211 Lecture 13, Slide 13 Preflight
A constant force acts for a time t on a block that is
initially at rest on a frictionless surface, resulting in a final
velocity V. Suppose the experiment is repeated on a block
with twice the mass using a force that’s half as big. For how
long would the force have to act to result in the same final
velocity? F
A) Four times as long.
B) Twice as long.
C) The same length.
D) Half as long.
E) A quarter as long. Lets try it again ! Physics 211 Lecture 13, Slide 14
Physics …The experiment is repeated on a block with twice the mass
using a force that’s half as big. For how long would the force
have to act to result in the same final velocity? F
A) Four times as long.
B) Twice as long.
C) The same length.
A) the change in momentum when the...
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 Spring '08
 Liss
 Energy, Kinetic Energy, Momentum, TA, Gold medal

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