What is the approximate rolling resistance of the toy train on the train track with a radius of 4mm? Can you calculate?

Explain the difference laminar and turbulent flow. explain it with the shear stress and the velocity profiles.

If you were designing a bumper for a car, would you prefer it to exhibit elastic or plastic deformation? why? consider the functions of a bumper in both a minor "fender-bender" and a major collision.

What precautions should you take to prevent injuries when dealing with heavy loads?