In a recent letter to this journal, Mungan noted that translational energy can be converted into gravitational potential energy when an object is projected vertically, but rotational energy is not usually converted in this manner. As an exception, he gave an example where “a ball initially rolling without slipping will travel higher up a rough ramp than it will up a frictionless ramp.” However, such a result is unlikely to be observed in practice. A better example would be a ball spinning rapidly forwards as it slides up the ramp, since the friction force on the ball then acts in a direction up the ramp.
References
1.
C. E.
Mungan
, “Impulse and work for the bullet-block Veritasium video
,” Phys. Teach.
53
, 325
–326
(Sept.
2015
).2.
R.
Cross
, “Rolling to a stop down an inclined plane
,” Eur. J. Phys.
36
, 065047
(2015
).3.
R.
Cross
, “Coulomb’s law for rolling friction
,” Am. J. Phys.
84
, 221
–230
(March
2016
).© 2017 American Association of Physics Teachers.
2017
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.