friction

The amount of friction depends on the normal force of the objects pressing together.

• True

• False

What type of friction is not moving?

• static
• sliding
• fluid
• rolling

F_N=100N, F_f=20N

• μ=5.0

• μ=0.2

• μ=1.2

• μ=0.1

What direction does friction act relative to motion?

• in the same direction
• in the opposite direction 
• need more information
• depends on the force

What is the coefficient of static friction if it takes 44 N of force to move a box that weighs 86 N? 

• 0.78
• 0.51
• 0.78 N
• 0.58 N

A box takes 40 N to start moving when the coefficient of static friction is .54. What is the weight of the box? 

• 81 N
• 18 N
• 98 N
• 74 N

When looking at friction problems, if the net force in the x-direction on an object is zero, what can we say about its acceleration?

• it is positive

• it is negative

• it is zero

• not enough information is given

Normal force is

• Always opposite the weight

• Always parallel and down the incline

• Always perpendicular to the surface

• It depends on the direction of motion

Friction is a force that acts in an ___________ direction of movement.

• similar
• opposite
• parallel
• west

Friction is a

• (a) non-contact force

• (b) contact force

• (c) magnetic force

• (d) electrostatic force