Force

Paper helicopters spin because of the earth’s gravity, lift, and configuration of the rotors. When dropped, the helicopter’s mass experiences gravity, and it naturally falls to the floor which causes paper blades to bend slightly upward due to lift. The lift force of the air pushes on each of the blades equally but in opposite directions, horizontally and vertically. As a result of the horizontal equal, opposite, and offset forces, the helicopter spins around as it descends.

When the bottle filled with water is dropped, the water and air inside the bottle will fall at the same rate due to gravity

Gravity is the force that attracts objects towards each other and the reason that everything that goes up must come down. Because the magnetic force between the magnet and the paperclip is stronger than the force of gravity between the paperclip and the ground, the paperclip remains in the air.

 According to Newton’s third law of motion, the walls of the balloon will exert an equal and opposite reaction force on the air molecules inside the balloon. This reaction force causes the balloon to expand and become inflated.

The coin-card experiment is a classic physics experiment that demonstrates the property of inertia of rest and frictional force.

Hooke’s law states that the strain in a solid is proportional to the applied stress within the elastic limit of that solid.