A roller coaster is designed such that riders experience ''weightlessness'' as they go round the top of a hill whose radius of curvature is 20 m. The speed of the car at the top of the hill is between

Sand is being dropped on a conveyer belt at the rate of M kg/s. The force necessary to keep the belt moving with a constant velocity of $$\upsilon $$ m/s will be :

Three forces acting on a body are shown in the figure. To have the resultant force only along the y-direction, the magnitude of the minimum additional force needed is

A block B is pushed momentarily along a horizontaly surface with an initial velocity V. If  $$\mu $$  is the coefficient of sliding friction between B and the surface, block B will come to rest after a time