Differentiate between weight and normal force.

Weight is the force due to gravity acting on an object, while normal force is the force exerted by a surface resisting gravity.

Weight is a force that is always directed towards the centre of the Earth. It is the force exerted on an object due to gravity and is calculated by multiplying the mass of the object by the acceleration due to gravity (9.8 m/s² on Earth). Weight is a vector quantity, meaning it has both magnitude and direction. It is dependent on the gravitational field strength of the location, hence, your weight would be less on the moon than on Earth due to the moon's weaker gravitational field.

On the other hand, the normal force is the force exerted by a surface to support the weight of an object resting on it. It acts perpendicular (or 'normal') to the surface. The normal force is what prevents solid objects from falling through each other. For example, when a book is placed on a table, the table exerts an upward normal force that balances the downward force of the book's weight, preventing the book from falling through the table.

The magnitude of the normal force depends on the angle of the surface. If an object is on an inclined plane, the normal force is less than the weight of the object because only a component of the weight acts perpendicular to the surface.

In summary, while both weight and normal force are forces acting on an object, they are different in their causes and directions. Weight is caused by gravity and is always directed downwards, while the normal force is caused by a surface resisting an object's weight and is always directed perpendicular to the surface. Understanding the difference between these two forces is crucial in solving problems involving forces and motion.