A50 kg boy is at the edge of a circular platform of radius 4.0 m which is rotating freely
at 0.5 rad s". the moment of inertia of the platform is 1000 kg m'. determine the new
angular velocity of the platform if the boy walks 1.0 m towards the centre of the
platform

When a charged balloon sticks to a wall, the downward gravitational force is balanced by an upward static friction force. the normal force is provided by the electrical attraction between the charged balloon and the equal but oppositely charged polarization induced in the wall's molecules. if the mass of a balloon is 1.2 g, its coefficient of static friction with the wall is 0.71, and the average distance between the opposite charges is 0.80 mm, what minimum amount of charge must be placed on the balloon in order for it to stick to the wall? express your answer to two significant figures and include appropriate units.