Understanding the Concepts

* Static Friction: This is the force that prevents an object from moving when a force is applied to it. It has a maximum value before the object starts to move.

* Coefficient of Static Friction (μs): This is a dimensionless number that represents the ratio of the maximum static friction force to the normal force.

* Normal Force (Fn): This is the force exerted by a surface perpendicular to the object in contact with it. On a level surface, the normal force is equal to the object's weight.

Calculations

1. Calculate the weight of the crate:

* Weight (W) = mass (m) * acceleration due to gravity (g)

* W = 40 kg * 9.8 m/s² = 392 N

2. Calculate the maximum static friction force:

* Maximum static friction (Fs) = μs * Fn

* Fs = 0.69 * 392 N = 270.88 N

Answer:

A horizontal force greater than 270.88 N is required to get the crate moving.