A4-meter plank weighing 7kg is lying on a dock with 3.02 meters of its length on the dock, and the rest of its length extending off the dock. if a child weighing 38kg walks out onto the part of the plank extending off the dock, what is the maximum distance in meters that the child can walk on the plank from the edge of the dock before he falls into the water?

Child can walk up to 0.18 m on the plank from the edge of the dock without falling into the water.

The child can only walk on the dock till the moment of the child mass is balanced by the weigh of the plank

Consider the free body diagram

Taking the moment about point O

38×d=7×1.02

d=0.18 m

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.