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## PowerPoint Slideshow about ' Static Friction' - deacon-rosario

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Holding in Place

- Objects on an incline will often stay put.
- There must be a force that holds the object in place.
- Static friction is from the contact of resting objects.
- Force holds up to a certain point
- Force is based on the type of contact (rough, smooth)
- Maximum force is proportional to the pressing force of the object (normal force)

Inequality

- The approximate formula for static friction is:
ms is the coefficient of static friction

- This is an inequality.
- The force of static friction is generally less than the coefficient times the normal force

q

Starting Motion- If Ffr < msFN = msmg cosq, then the block will hold.
- At equality the block just begins to move.

Use a pulley and vary the weight to see when movement begins.

Forces balance on mass 1

Tension is equal on the rope

Forces balance on mass 2

m1

m2

Measuring Friction: PulleyFT

Frope

FT

Frope

The pulley determines the coefficient of friction through the ratio of masses.

m1

m2

Coefficient of Friction: PulleyUse an incline and vary the angle to see when movement begins.

One component of gravity balances the normal force

The other component of gravity balances friction

m

q

Measuring Friction: InclineThe incline determines the coefficient of friction through the tangent of the angle.

m

q

Coefficient of Friction: InclineNormal Force and Friction the tangent of the angle.

- Static friction depends on both the normal force and on the coefficient of friction.
- To reduce friction requires reducing one of those factors.
- Reduce normal force by lightening the load
- Reduce normal force by adding additional upward force
- Add a lubricant to reduce the coefficient of friction

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