WARM UP: Please grab your sheet from yesterday. –Finish the WEIGHT calculations from the FRONT by multiplying your mass in NEWTONS by the GRAVITATIONAL FORCE on each planet –Complete the backside of the sheet by diving the weight on each planet by Nicki Minaj’s mass (50 kg). CALCULATED FROM THE INFO ON PLANET EARTH…

Announcements Turn HW into the blue bin Turn in signed progress reports into the blue bin SELL SOME FRUIT DO NOT WALK OUT OF CLASS WITHOUT TURNING YOUR NOTEBOOK IN

Notebook Quiz 1.What is the definition of POSITION? 2.What is the unit of FORCE? 3.What is the formula to calculate speed? 4.What do you plot along the Y-axis on a Distance-Time graph?

FRICTION

FRICTION What will happen when the ball is released? When the ball reaches the bottom of the slope, will it keep moving forever? Since the ball stops, there must be a force acting to slow the ball down. The force that slows the ball to a stop is FRICTION.

What is Friction? Friction is a force that two surfaces exert on each other when they rub against each other. The direction of the friction force is always OPPOSITE to the direction of the motion. Friction Force Direction of Motion

Types of Friction Fluid friction occurs when a solid object moves through a liquid or gas. Air resistance is a type of fluid friction. Friction Force Direction of Motion

Types of Friction Sliding friction occurs when two solids slide over each other. Sliding friction makes car brakes work and stops athletes from slipping. Direction of Slide Sliding Friction Force

Types of Friction Rolling friction occurs when an object rolls across a surface. Rolling friction is easier to overcome than sliding friction for the same materials. Friction Force Direction of Motion

Types of Friction Static Friction opposes the motion of an object that is at rest To make the object move, you have to exert a force larger than the force of static friction. Direction of Intended Movement Static Friction Force

Which type of friction is slowing down the object in each situation? You are slipping down a waterslide at Treasure Island in Orlando! You use a lot of force to slide a desk across the floor. You’re riding a skateboard down the street and it slowly rolls to a stop. You try to push the couch, but can’t seem to move it. Friction Force SLIDING FRICTION ROLLING FRICTION FLUID FRICTION STATIC FRICTION

LAB PRACTICE! MU OF THE SHOE!!!

EXIT TICKET 1.What happens when you wear socks and walk on a wood or tile floor? Why do you think this happens? 2.What causes a baseball or football to slow down in the air? 3.How many forces are acting on you when you sleep? How many forces are acting on you when you sit in class?