Friction in Connected and Stacked Bodies
For no slip, bodies share acceleration and |f_required| <= mu_s N; after slip use kinetic friction.
Why this shows up in the exam
Stacked blocks · Rough connected systems · Multiple contacts
Learn the idea
Find common acceleration first, then test the friction required at each contact. Friction may be the only force accelerating one layer of a moving stack.
🧠 Memory hook: Whole system for a; one layer for f.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- a_common = F_ext/M_total — together motion
- f_required = m_layer a_common — undriven layer
- |f_required| <= mu_s N — no-slip test
How to approach it
- 1Solve whole system
- 2Isolate a layer
- 3Check every static limit
Common slip-ups that cost marks
- •Using limit before requirement
- •Missing ground friction
- •Same direction on both contact partners
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A 2 kg block moves on a horizontal rough surface with coefficient of kinetic friction 0.2. A horizontal force of 10 N acts on it. Take g = 10 m/s^2. What is its acceleration?
More from Laws of Motion
Newton's laws of motion
Understand and apply Newton's first, second, and third laws to analyze forces, motion, and interactions in various physical situations.
Circular motion and centripetal force
Analyze the forces involved in uniform and non-uniform circular motion, including centripetal force, tension, and friction.
Friction and its applications
Study the types of friction (static and kinetic), their effects on motion, and how friction interacts with other forces in different scenarios.
Impulse, momentum, and conservation laws
Explore the principles of linear momentum, impulse, and their conservation in collisions and explosions.
Inertia and Inertial Frames
In an inertial frame, sum F_ext = 0 implies a = 0. Earth-fixed frames are approximate when rotational effects are negligible.
Newton’s Second Law in Vector Form
In an inertial frame sum F_ext = dp/dt; for constant mass this becomes m dv/dt = ma.