At rest, yet forces act

The idea

An object at rest may still have forces acting on it; being at rest means the forces acting on it are balancing one another.

A book on a table

A book lies still on a table.

Is any force acting on the book?

• Yes, but the forces balance each other
• No force at all
• Only one force

Balance the pushes

Make the push from the left equal to the push from the right. Both must be more than zero.

Balanced forces

With equal pushes the box stayed at rest, but two forces were acting on it. When an object is at rest, the forces on it are balancing one another.

An object at rest may still have forces acting on it. Being at rest means the forces acting on it are balancing one another.

Notes

An object at rest may still have forces acting on it. At rest means the forces on it are balancing one another.

Check yourself

An object is at rest. This means that …

Two equal pushes act on a box from opposite sides. The box …

Does an object at rest always have no force acting on it?

• no force can ever act on it. Forces may be acting. They balance one another.
• the forces on it balance each other — correct. Yes!
• it has run out of forces. Forces do not run out. They are balancing.
• moves to the left. The two pushes balance each other, so the box stays at rest.
• moves to the right. The two pushes balance each other, so the box stays at rest.
• stays at rest — correct. Yes!
• No, forces may act and balance each other — correct. Yes!
• Yes, never any force. The forces may be balancing one another.
• Yes, because it is not moving. It is at rest because the forces balance, not because there are none.