Friction

• Friction – a force that opposes motion between 2 surfaces that are touching.– Always acts in a direction opposite to the

motion of the object.– The greater the friction, the faster an object

will lose speed.

FRICTION

TYPES OF FRICTION EXPLANATION

Sliding A hockey puck crossing an ice rink

Rolling A wheeled cart being pushed

Fluid Air rushing past a speeding car

Static A crate resting on a loading ramp

Energy of Motion

• Kinetic Energy – Energy in a moving object. – More speed or more mass = more kinetic

energy• Potential Energy – Energy stored in an

object because of position– High diver on the board – lots of potential

energy– Becomes kinetic energy when he dives!

Mass vs. Weight• Mass = amount of matter in an object• Weight = force of gravity on an object

– NOT THE SAME THING!!!– Weight = gravity x mass

On Earth

Weight = 120 lbsMass = 46.36 kg

On the Moon

Weight = 20 lbsMass = 46.36 kg

In Space

Weight = 0 lbsMass = 46.36 kg