Static Friction

Part of the Mechanics section of Coddy's Physics journey. Lesson 16 of 97.

Push gently on a heavy crate and it stays put: static friction pushes back exactly as hard as you push, up to a limit:

$f_s \le \mu_s N$

Push harder than $\mu_s N$ and the crate starts to slide.

Graph of friction f against the push F for a 50 kilogram crate: friction rises along with the push up to 196 newtons, then drops to a constant 147 newtons once the crate slides

Static friction matches the push up to its limit, $196\ \mathrm{N}$ . Once the crate slides, friction is lower.

Challenge

A $30\ \mathrm{kg}$ crate rests on a floor with $\mu = 0.4$ for static friction. Find the smallest push $F$ to the right that starts it sliding.

Try it yourself

Solve for $F$

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Mechanics

1Introduction

What is Physics?Your First Equation Turning a Rule Around

4Inclined Planes

Forces on an Incline Gravity Components Frictionless Incline Incline with Friction Will It Slide?Recap - Ramp Challenge

7Projectile Motion

Independent Axes Horizontal Launch Launch at an Angle Range and Max Height Recap - Hit the Target

10Work and Energy

Work Kinetic Energy Work-Energy Theorem Gravitational PE Conservation of Energy Power Recap - Roller Coaster

13Impulse and Momentum

Momentum Impulse Conservation of Momentum Elastic Collisions Inelastic Collisions Recap - Air Track

16Simple Harmonic Motion

What is SHM?Mass on a Spring The Pendulum SHM Graphs Energy in SHM Recap - Oscillator

3Friction

What is Friction?Static FrictionKinetic Friction Friction and Newton's Laws Recap - Sliding Crate

6Vertical Motion

Free Fall Throwing Upward Time in the Air Recap - Dropped Ball

9Project: Delivery Drone

Mission Briefing Takeoff Thrust Climb to Altitude Cruise and Brake Package Drop

12Elastic Energy

Elastic Potential Energy Spring Launchers Energy with Springs Recap - Spring Launcher

15Circular Motion

Uniform Circular Motion Centripetal Acceleration Horizontal Circles Vertical Circles Loop the Loop Recap - Car on a Curve

18Final Challenges

Recap - Stunt Ramp Recap - Crash Test Recap - Space Probe