Chapter 10- Forces Force A push or pull that one thing exerts on another Arrows used to describe strength and direction Measured in Newton’s (N) Two Types: 1.Unbalanced- one force is stronger than the other 2.Balanced- forces with the same strength

Forces on Earth 1.Friction Force between two surfaces/objects that are touching each other

smooth surface= less friction rough surface= more friction

Three Types of Friction: a. static- affects objects that are NOT moving b. sliding- occurs when two objects are slid across each other c. rolling- affects objects that roll

2. Gravity The force that pulls objects to the ground Newton and the apple story Amount of Gravity is affected by: -Mass (size): the bigger the object, the more gravity it makes -Distance: the closer objects are, the more gravity they experience

Weight vs. Mass Gravity’s pull gives things weight The stronger the gravity…..the more you weigh Your Weight on Other Worlds | Exploratorium

Gravity and Moving Objects Objects accelerate as they fall Acceleration of all falling objects equals 9.8 m/s 2 Does everything fall the same? HowStuffWorks Videos "Assignment Discovery: Aristotle Galileo and Gravity"

3.Air Resistance Force that moving objects experience The faster the speed= the more air resistance Fights gravity’s pull Feather & Hammer Drop on Moon - YouTube

Terminal Velocity (speed) Fastest speed an object falling through the air can reach Created by a balance between gravity and air resistance TV of a human= 124 miles per hour Until Felix Baumgartner….

Newton’s Laws Newton’s 1 st Law Objects at rest stay at rest and objects in motion stay in motion (unless “outside” forces act on them)

Inertia Used to describe Newton’s 1 st Law Objects resist change- hard to get them to start moving and hard to stop them More mass= more inertia

Newton’s 2 nd Law Objects move and accelerate in the direction of the greatest force Formula:F= m x a Practice Problem: How much force is needed to accelerate a 2g golf ball 30m/s 2 ?

Newton’s 3 rd Law For every action there is an opposite but equal reaction

Momentum The strength of an object’s movement No movement….no momentum (has to be moving) More mass=more inertia=more momentum Formula:P= m x v Practice Problem: Calculate the momentum of a 11.35kg wagon rolling down a hill at 12m/s?

Conservation of Momentum Momentum of objects stays the same unless “outside” forces act on them

Projectiles Anything thrown through the air Horizontal movement- throw Vertical movement- gravity Vertical + Horizontal = curved path