Forces are fundamental interactions that can cause objects to move or change their shape. Gravitational force attracts objects towards the Earth, as seen in the falling of an apple. Frictional force opposes motion between surfaces, like the resistance felt when sliding a book across a table. Magnetic force causes attraction or repulsion between magnetic objects, evident in the interaction between a magnet and iron filings. Electrostatic force occurs between charged particles, such as the static cling of clothes removed from a dryer. Tensional force is transmitted through a rope or string under tension, like in a game of tug-of-war. Normal force supports the weight of objects resting on surfaces, preventing them from falling.