A cart of mass 3 kg is pulled by a 5 kg object as shown in figure. Length of cart is 40 cm moves on frictionless table. There is a small brick of mass 2 kg on the cart which falls at 0.8 sec. after the start of motion. if the coefficient of friction between cart and brick is `(x)/(10)`. then value of x is `:(g=10m//s^(2))`