#### Transcript FRICTION A crate resting on a loading ramp Static Air rushing past a

```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
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
In Space
On Earth
Weight = 120 lbs
Mass = 46.36 kg
Weight = 0 lbs
On the Moon
Mass = 46.36 kg
Weight = 20 lbs
Mass = 46.36 kg
```