Static Friction

Justine places the pile of books on the table. What friction is being shown?

• fluid friction

• static friction

• rolling friction

• sliding friction

Why does static friction exists?

• Because surfaces are smoother when you move an object

• Because surfaces are smoother before you move an object

• Because surfaces have imperfections and adhesion occurs between the two

  stationary surfaces

• Because surfaces have imperfections but adhesion does not occur between the two

  stationary surfaces

Which of the following statements is TRUE?

• Static friction results when moving objects or rough surfaces rub together.

• Static friction occurs in a swimmer swimming in water or a boat travelling in water.

• Static friction occurs between two objects that are in motion against each other.

• Static friction occurs when two objects rub against each other or slide against.

Which of the following is an example of static friction?

• Rubbing both hands with each other

• Feet against the ground when walking

• The wheels of a bicycle against the ground

• A heavy box against the ground that difficult to lift and move

Why is it more difficult to start moving a heavy object than to keep it moving?

• Static friction is greater than sliding friction.

• Sliding friction is greater than static friction.

• Rolling friction is greater than static friction.

• Fluid friction is greater than sliding friction.

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DOK Level 3: Strategic Thinking

Why do you need to apply more force to start moving an object from rest compared to keeping it moving?

• Static friction is generally higher than kinetic friction

• Kinetic friction is generally higher than static friction

• Objects gain energy when they start moving

• Objects are lighter when in motion

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DOK Level 2: Skill/Concept

David is trying to push a heavy box across the floor. Why does he find it more difficult to start moving the box than to keep it moving once it starts sliding?

• Static friction is greater than sliding friction.

• Sliding friction is greater than static friction.

• Rolling friction is greater than static friction.

• Fluid friction is greater than sliding friction.

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DOK Level 3: Strategic Thinking

What is the force that opposes the relative motion or tendency of such motion of two surfaces in contact?

• Gravity

• Friction

• Magnetism

• Tension

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DOK Level 1: Recall

Which of the following words implies no motion?

• force

• friction

• gravity

• static

Static friction prevents motion between surfaces in contact.

• True

• False