Friction

Question 1

What is friction?

Answer 1

Friction is a contact force that resists motion between 2 objects that are touching.

Question 2

In what direction does friction act?

Answer 2

Friction always acts parallel to the surfaces in the opposite direction to movement.

Question 4

What are the 2 types of friction?

Answer 4

Static friction and Kinetic friction.

Question 5

Describe static friction

Answer 5

Static friction, which exists between a surface and a stationary object. Static friction increases to match the other force/s, but only up to a point.

Question 6

Describe kinetic friction

Answer 6

Kinetic friction, which exists between a surface and a moving object. Kinetic friction is approximately constant, and always less than the maximum static friction

Question 7

What is the formula for friction and identify the variables.

Answer 7

𝐹_f =𝜇𝐹_N
Fn is the normal force, 𝜇𝐹 is the coefficient of friction and Ff is the frictional force.

Question 8

What are the coefficients of static and kinetic friction, and describe their magnitudes in comparison to one another.

Answer 8

𝜇_s, the coefficient of static friction
𝐹_s ≤ 𝜇sFn

𝜇_k , the coefficient of kinetic friction (which is always lower than 𝜇_s)
𝐹_k = 𝜇k𝐹n