3. From a circular plate of a diameter 6 cm is cut out a circle whose diameter is equal to the radius of the plate. The C.G. of the remainder from the centre of circular plate is at a distance of
4. A block of weight 50 kg is placed on a horizontal plane. When a horizontal force of 18 kg is applied, the block is just on the point of motion. The angle of friction is
8. A train weighing 196 tonnes experiences a frictional resistance of per tonne. The speed of the train at the top of a down gradient 1 in 78.4 is 36 km/hour. The speed of the train after running 1 km down the slope, is
9. If a particle moves with a uniform angular velocity ? radians/sec along the circumference of a circle of radius r, the equation for the velocity of the particle, is