The Nature of Forces Chapter 11

Force A force is a push or pull A force gives energy to an object sometimes causing it to start moving, stop moving, or change directions. Force is measured in Newtons (N)

Combining Forces If forces go in the same direction - add together 10 N + 10 N = 20 N to the right If forces go in opposite directions - subtract 10 N 15 N = 5 N to the left

Friction Friction is a force that opposes motion Causes a moving object to slow down and eventually stop Lubricant - reduces friction Examples: oil, wax, water, wheels, axles

Friction

Newton’s 1st Law of Motion 1st Law states that objects in motion stay in motion and objects at rest will stay at rest Inertia - objects have a tendency to remain in motion or stay at rest

Newton’s 2nd Law of Motion The 2nd Law demonstrates how mass, force and acceleration are related Force = mass x acceleration

Newton’s 3rd Law of Motion The 3rd Law states that for every action there is an equal and opposite reaction All forces come in pairs

Newton’s Laws of Motion

Gravity Gravity is a force of attraction between two objects The larger objects “pulls” smaller object towards them All objects on Earth are pulled toward the core

Falling Objects All objects near the Earth’s surface fall at a rate of 9.8 m/sec/sec Air resistance - opposes downward motion of objects Objects with greater surface area have greater resistance

Falling Objects