Friction Practice Set 2
10 problems · instant feedback · full explanations
Friction always opposes relative motion between surfaces. Draw the free-body diagram first, find the normal force, then apply f = μN.
Q1.
How do static and kinetic friction typically compare for the same two surfaces?
Multiple choice · Easy
Q2.
A 10 kg crate slides across a floor with μk = 0.3. What is the kinetic friction force? (Use g = 9.8 m/s².)
Numerical answer (N) · Easy
Q3.
A 20 kg box sits on a floor with μs = 0.5. What is the largest horizontal push that will NOT move it? (Use g = 9.8 m/s².)
Numerical answer (N) · Medium
Q4.
A box slides backward across a truck bed that is accelerating forward. Which way does kinetic friction act on the box?
Multiple choice · Medium
Q5.
What minimum coefficient of static friction keeps a block at rest on a 30° incline?
Numerical answer · Hard
Q6.
A car wheel rolls without slipping. What kind of friction acts at the contact patch?
Multiple choice · Easy
Q7.
Friction always acts opposite to the direction an object is moving.
True / False · Medium
Q8.
Kinetic friction is approximately independent of the contact area between the surfaces.
True / False · Easy
Q9.
A 5 kg box is pulled with 30 N across a floor with μk = 0.4. What is its acceleration? (Use g = 9.8 m/s².)
Numerical answer (m/s²) · Hard
Q10.
Why do locked, skidding brakes stop a car less effectively than rolling brakes?
Multiple choice · Medium