Why does the box stop?
F=MA
Friction is the force resisting
the motion of objects sliding
against each other.
Box
Surface
Friction is a force!
Force
FrictionF=MA
Force
Three types of friction
Static Friction
Static
means
“no motion”
Static
friction
is the friction force that prevents two
surfaces at rest from sliding past each other.
Apply
ForceForce
Friction
As you apply
force, friction
force increases
When applied force is greater than friction force,
the object begins to move
Three types of friction
Sliding Friction
Sliding friction is the friction force that opposes the
motion of an object along a surface.
Static friction is before an object moves
Sliding friction is when the object is in motion
Three types of friction
Rolling Friction
Rolling friction is the friction force that opposes the
motion of a circluar object along a surface.
Three types of friction
Static Friction
> Sliding Friction > Rolling Friction
All friction opposes motion
Equation
𝐹𝑓𝑟𝑖𝑐𝑡𝑖𝑜𝑛 = 𝜇 ∗ 𝑀 ∗ 𝑔
Newton’s First Law
• Also called: Newton’s Law of Inertia
• Inertia is the resistance to motion due to mass
More Mass = More Inertia
Example
Elephant has more inertia ‘
than a human
Which means, it’s harder to
change an elephant’s motion than
a human’s motion.
More inertia, means more force to get it moving
50 kg
Force
More Mass = More Inertia
100 kg
2 x Force
More Inertia = More Resistance
150 kg
3 x Force
Friction Force
• Depends on surface and shape of object
Inertia
• Depends on mass of the object