2/10 & 2/11 - 8th Grade Agenda Learning Objective: Learn about Friction Collect HW: Reading & Notetaking p.172 – 173 Springs Scales Lab Textbook Reading p. 380 - 383 HW: Reading & Notetaking p.175 – 176 Reminder Science Fair Board due 2/24 (50 Points)

Daily Reflection Prompt: Write your own definition of “Force”.

In Science, a force is a P____ or a P_____ ush ull

Force can be described by S_________ and D_________ trength irection

When two forces act in the same direction, they A___ together dd The combination of all forces acting on an object is called the net force

Which way will this object move? Unbalanced force will cause a change in velocity

A nonzero net force, which changes an object’s motion is Un_________ Force balanced

Which way will this object move? Balanced forces acting on an object do not change the object’s velocity.

Equal forces acting on one object in opposite directions are called B______ Force alanced

Adding a force acting in one direction to a force acting in another direction is same as adding a P______ number and a N______ number. ositive egative

The overall force of an object after all the forces are added together is called N___ Force

For an object to stay in motion, a F_____ has to act on it. orce

The force that one surface exerts on another when the two rub against each other is called … F________ riction

Friction act in a direction O_________ to the object’s direction of motion. pposite

The strength of the force of friction depends on two factors Type of surfaces involved How hard the surfaces push together

How is friction useful in helping you walk? Without friction your shoes would only slide across the floor, and you would never move forward.

What is static friction The friction that acts on objects that are not mov______ is called static friction. Because of static friction you must use ext_____ force to start the motion of stationary objects. ing ra

What is sliding friction Sliding friction occurs when two solid surf______ slide over each other. When you stop a bicycle with hand brakes, sliding friction is stop______the bike. ace ping

What is rolling friction When an object rolls across a surf______, rolling friction occurs. Engineers use ball bearing to reduce the friction between the wheels and the skate________ ace board

What is rolling friction Fluids, such as water, oil or air are materials that flow eas______. Fluid friction occurs when a solid object moves through a fluid. Fluid friction is usually less than sliding fric______. ily tion