contact forces

Contact forces are forces that act only when objects touch each other, either directly or through something connecting them.

• When you push a door, your hand touches the door and changes its motion. This is a contact force.
• A rope can transmit a contact force: when you pull a bucket from a well, your hand pulls the rope, and the rope pulls the bucket.
• Common contact forces include muscular force (from our muscles), friction (between rubbing surfaces), and the supporting push of a table on a book.
• Contact does not always mean skin-to-object contact. A bat hitting a ball, tyres gripping a road, and a magnet attached to a fridge all involve objects touching.
• These forces help us walk, write, lift objects, stop a bicycle, and hold things in place in everyday life.