5 questions about force (urgent) 10 marks

1) & 2) Frictional force exist in a pair of forces, i.e. action and reaction forces.

3) A car moving forward encounter frictional force which opposes the motion of the car. But, the frictional force exerted by the ground applies on the rolling wheel and keeps the wheel rolling. If the frictional force is too small, i,e, on the icy surface, the wheels cannot rotate and only skid on the icy surface. When the wheel rotate, the reaction force is also applied by the wheel to the ground. But, it has negligible effect on the ground due to the enormous mass of the Earth.

4) The speed of the trolley depends only on the force exerted on the rope. If the forces exerted by the man on the rope in both cases is of the same magnitude, the trolley moves at the same speed in both cases. When the two man are pulling the rope at the same time, they are only applying the forces of same magnitude in opposite direction.

5) When the rocket eject water/air, the reaction force will propel the rocket forward.