# Given a wall-mounted cantilever beam, describe the shear force diagram and bending moment diagram

Additionally, how would you reduce deflection? Where and what is the equation for max. deflection?

This is a question asked in Apple’s very first technical phone screen. It’s important to know the basics which is why they ask you almost immediately!

The location of maximum deflection is at the free end of the beam, and the max bending moment is at the fixed interface between the wall and cantilever beam.

Try to memorize the basic equations for max deflection:

Max Deflection = (P*L^3) / 3*EI

P = Load
L = Length
E = Modulus of Elasticity (Material Property)
I = Area Moment of Inertia (Depends on the cross-section)

How would you manipulate the above equation to minimize deflection?

Shouldn’t the bending moment diagram be Negative since the beam is hogging?

@bmachado, I would agree that the bending moment diagram should be negative. My knowledge of statics is pretty rusty (to be completely honest). Seems as though the BMD should be inverted negatively.