When you're looking for quality mechanical engineering services, you don't want an amateur on the job. You want a mechanical engineer who knows his stuff and has the chops to prove it.

You need someone who knows the basics -- someone who won't look puzzled when it's time to make unit conversions, or when you mention terms like "conservation of momentum."

Great mechanical engineering services are about expertise. In that regard, here are five questions to spring on any mechanical engineer you may be interviewing.

So, acceleration... Is that a vector quantity or a scalar quantity? A good provider of mechanical engineering services knows his vectors and scalars, and knows that acceleration -- an expression in the change in velocity of an object -- is a vector quantity, meaning it has two independently variable properties: Magnitude and direction. Scalars are one-dimensional, and their quantities can be depicted on a line.

How do you suppose you'd go about determining the mass of this delicious apple? Here it helps to have an apple handy so the mechanical engineer in question doesn't think you're crazy. Determining mass should be easy for any accomplished mechanical engineer -- simply set the object to oscillate between a pair of springs in a weightless environment, and measure the resultant oscillation of the springs. Of course, you could also simply place the object in a scale, but that would only measure the mass within Earth's gravitational field. So if you're contracting these mechanical engineering services to design a device that'll be leaving earth, you may want an engineer who knows a more sophisticated method.

What two variables would you multiply together to determine a moving object's momentum? Like acceleration, momentum is a vector, so it comprises two independent variables. To determine momentum, you'd multiply an object's mass by its speed. Thus, a Toyota moving at 80 kilometers per hour would have more momentum than a Jack Russell terrier sliding across a linoleum floor.

What's the simple term for the quantitative expression of the average kinetic energy contained in a given item? The correct answer here is temperature. For any given substance, the higher the temperature, the faster the atoms and molecules within that substance are moving around.

What's the standard unit of measurement for power? How about energy? What about planar angular measure? Good mechanical engineering services include a comprehensive knowledge of units of measurement. Power is measured in watts. Energy is measured in joules. And the standard unit of planar angular measure is the radian.