At a sudden contraction in a pipe the diameter changes from d1 to d2. the pressure drop, δp, which develops across the contraction is a function of d1 and d2, as well as the velocity, v, in the larger pipe, and the fluid density, and viscosity, use d1, v, and as repeating variables to determine a suitable set of dimensionless parameters. why would it be incorrect to include the velocity in the smaller pipe as an additional variable?

The objects are acted upon by only one force. gravity. mass times the acceleration of gravity (-9.81meters/second squared).

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Ithink it’s: light bounce if off a mirror