Suppose a block of mass m1 traveling at speed v1 makes a one-dimensional perfectly inelastic collision with another block of mass m2. What else does one need to know to calculate the fraction of the mechanical energy that is dissipated in the collision?
REFERENCES
1.
J. W.
Zwart
, “A safe and inexpensive ballistic pendulum
,” Phys. Teach.
25
, 447
–448
(Oct. 1987
).2.
In a perfectly inelastic collision, dP/dt only reduces to d(mv)/dt if the collected mass elements have zero initial momentum, which is equivalent to in
J.
Mallinckrodt
, “F doesnot equald(mv)/dt
,” letter to the editor, Phys. Teach.
48
, 360
(Sept. 2010
). For example, holds for a raindrop falling through stationary mist (because the mist has zero initial momentum) as in
C. E.
Mungan
, “More about the falling raindrop
,” Am. J. Phys.
78
, 1421
(Dec. 2010
). In contrast, it does not hold for a horizontally moving funnel adding sand into a cart (because the sand is initially moving with the cart's velocity) as in
W.
Kunkel
and R.
Harrington
, “Modeling the motion of an increasing mass system
,” Phys. Teach.
48
, 243
–245
(April 2010
).© 2013 American Association of Physics Teachers.
2013
American Association of Physics Teachers
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