A boy is sitting on a chair placed on the floor of a room. Write as many action reaction pairs of forces as you can.

A block is placed on the horizontal surface. There are two forces acting on the block. One, the downward pull of gravity and other a normal force acting on it. Are these forces equal and opposite? Do they form action - reaction pair? Discuss with your friends.

Assertion :- A block is hanged from spring. Spring force on block gravitational force on block are not action and reaction pair. Reason :- Action and reaction force acts in opposite direction.

A wooden chair is dragged on the level floor and brought to the same place. Let the distance covered be 's' and frictional force acted on the chair by the floor be 'f' . What is the work done by the frictional force

Assertion: Pseudo force is an imaginary force which is recongnised only by a non-inertial observer to explain the physical situation according to newton's laws. Reason: Pseudo force has no physical origin, that is it is not caused by one of the basic interactions in nature. It does not exist in the action-reaction pair.

A wooden block of mass 2 kg rests on a soft horizontal floor. When an iron cylinder of mass 25 kg is placed on top of the block, the floor yields steadily and the block and the cylinder together go down with an acceleration of 0.1 m s^(-2) . What is the action of the block on the floor (a) before and (b) after the floor yields ? Take g = 10 m s^(-2) . Identify the action-reaction pairs in the problem.

A bullet of mass 50g moving with velocity 600m//s hits block of mass 1.0kg placed on a rough horizontal ground and comes out of the block with a velocity of 400m//s . The coefficient of friction between the block and the ground is 0.25 . Neglect loss of mass of the block as the bullet pierces through it. (a) In spite of the fact that friction acts a an external force, can you apply principle of conservation of momentum during interaction of the ullet with the block? (b) Find velocity of the block immediately after the bullet pierces through it. (c)FInd the distance the block will travel before it stops.

A tea party is arranged for 16 persons along two sides of a long table with 8 chairs on each side. Four persons wish to sit on one particular and two on the other side. In how many ways can they be seated?

A rope placed straight on a frictionless floor is pulled longtudinally by a force F. Tension force 7^(@) developed in the rope at a point varies with distance x of the point from the rear end as shown in the graph. What can you certainly conclude about density of the rope?