Which law is to be used by a man stranded at the middle of a pond, when no friction is experienced by the boat?

Two light posts of equal heights stand on either side of a pond which is 100meters wide.From a boat in the pond between the posts the elevation of the tops of the post are found to be 60^@ and 30^@ .Find the height of the posts and the position of the posts.

A man sitting at a height of 20m in a tall tree on a small island in the middle of the river observes two poles directly opposite each other on the two banks of river and in line with the foot of the tree. If the angles of depression of the feet of the poles from a point at which the man is sitting on the three on either side of the river are 60° and 30° respectively. Find the width of the river.

When a boat is moving in the river, does the water offer force of friction to its movement ?

Find the time in which a layer of ice 3 cm thick on the surface of a pond will increase in thickness by 1 mm when the temperature of the surrounding is -20°C .the thermal conductivity of ice is 2.1 W/m K, latent heatof ice 3.36 10^5J/kg and density is 900 kg/m^-3 .

A 70 kg man stands in contact against the inner wail of a hollow cylindrical drum of radius 3 m rotating about its vertical axis with 200 rev/min. The coefficient of friction between the wall and his clothing is 0.15. What is the minimum rotational speed of the cylinder to enable the man to ' remain stuck to the wall (without falling) when the floor is suddenly removed?