FORCES What is a force A force is

FORCES

What is a force? • A force is a PUSH or a PULL. • Forces do not have mass nor do they occupy a space. • Forces can – tear, bend, twist, or stretch an object. – Change the direction of the motion • Measured in Newtons (N)

2 main types of forces • Contact forces – A force between two objects in direct contact with one another. v. Frictional • Non-Contact forces – Forces that can act on objects at a distance and between two objects which are not in direct contact with one another. v. Magnetic v. Gravitational

Gravitational Force • Pulls objects towards the center of the earth • Objects exert a force of attraction on all objects around it. – The force may be small that we can’t feel it. • The larger the mass, the stronger the gravitational force – The sun’s gravitational force pulls smaller bodies towards it • The closer the two objects are, the stronger the gravitational force

Gravitational force • Objects fall to the ground at the same rate, regardless of their mass in the absence of air • Overcoming gravity: – Energy is needed to overcome gravity – More energy if you’re going against it – Less energy if you’re going towards it.

Gravitational energy in our daily lives

Frictional Force • A force that opposes motion. • Produced when two surfaces are in contact with each other • Can cause an object to move slower • More friction is exerted if the object’s mass is great • Surfaces play a role in the amount of friction generated

Frictional Force • Types of friction – Sliding • Two solid objects with one object sliding over the other • snowboarding – Rolling • When a circular object rolls over a surface • cycling – Fluid • Involves a solid object moving through a wet or fluid (liquid or gas)surface • Parachuting, wakeboarding

Infer the friction generated in the given pictures

Frictional energy • Energy is required to overcome friction. • How much energy is needed to overcome friction over smoother surfaces? • How much energy is needed to overcome friction over rougher surfaces? • When is frictional energy beneficial? When is frictional energy harmful?

Frictional energy in our lives

Magnetic Force • A force of attraction that pulls unlike poles. • A force of repulsion that pushes like poles. • A MAGNET attracts magnetic materials, which include those made up of Iron, steel, cobalt and nickel

Magnetic force • A stronger magnet exerts a stronger force of attraction – The material may move faster – A stronger force is needed to overcome a stronger magnet N S

Magnetism in our daily lives

The PENDULUM String e c n ta is s e ir r A Metal ball gravity

The PENDULUM • Found in clocks; has a weight and a string • Air resistance (frictional force) and gravity affect the motion of the pendulum • The length of the string also affects the time for the pendulum to complete its swings