- #1
superdave
- 150
- 3
Block B, of mass m_B, rests on block A, of mass m_A, which in turn is on a horizontal table top View Figure . The coefficient of kinetic friction between block A and the table top is mu_k and the coefficient of static friction between block A and block B is mu_s. A light string attached to block A passes over a frictionless, massless pulley and block C is suspended from the other end of the string.
http://session.masteringphysics.com/problemAsset/1007012/5/yf_Figure_5_66.jpg
What is the largest mass m_C that block C can have so that blocks A and B still slide together when the system is released from rest?
Okay, I get:
a = [m_c *g - (m_a + m_b)*g * mu_k]/(m_a + m_b)
and the max a is m_b * g * mu_s.
I set them equal, and end up with
m_c = (m_a + m_b)(mu_k + mu_s * m_b)
but that isn't correct. help?
http://session.masteringphysics.com/problemAsset/1007012/5/yf_Figure_5_66.jpg
What is the largest mass m_C that block C can have so that blocks A and B still slide together when the system is released from rest?
Okay, I get:
a = [m_c *g - (m_a + m_b)*g * mu_k]/(m_a + m_b)
and the max a is m_b * g * mu_s.
I set them equal, and end up with
m_c = (m_a + m_b)(mu_k + mu_s * m_b)
but that isn't correct. help?