A cart of mass m1 m_1\,m1 is pulled along a frictionless horizontal track by a thin string connected over a frictionless pulley to a hanging object of weight FgF_gFg. Only the gravitational force acts on the hanging object, and friction is negligible. The acceleration of free fall is ggg.
Which of the following is the correct expression for the acceleration a a\,a of the cart?
a=Fgm1a = \frac{F_g}{m_1}a=m1Fg
a=Fg2m1a = \frac{F_g}{2m_1}a=2m1Fg
a=Fgm1+Fgga = \frac{F_g}{m_1 + \frac{F_g}{g}}a=m1+gFgFg
a=ga = ga=g