A student of mass stands motionless on a frictionless cart of mass while holding a…

PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion

Problem

A student of mass

m_s

stands motionless on a frictionless cart of mass

m_c

while holding a puck of mass

m_p

. The entire system is initially at rest relative to the ground. The student then throws the puck straight forward so that the puck leaves the student’s hand with speed

v_0

relative to the ground. Air resistance is negligible. (a) Derive an expression for the speed

v_{\text{cart}}

of the cart + student system immediately after the puck is released. Express your answer in terms of

m_s

m_c

m_p

, and

v_0

. (b) Evaluate

v_{\text{cart}}

numerically for

m_s = 60\,\text{kg}

m_c = 20\,\text{kg}

m_p = 4.0\,\text{kg}

, and

v_0 = 5.0\,\text{m}\,\text{s}^{-1}

. (c) Determine the total kinetic energy of the entire system (cart + student + puck) before the throw and immediately after the throw. State whether the kinetic energy increased, decreased, or stayed the same, and provide a physical explanation for the change observed.

Related theory

Browse the problem library