Physics Question

JibsGuy52

2+ Year Member
Could someone explain this question to me? I don't get how they got that formula in the slightest (Spoiler:Second picture contains the answer for anyone wanting to attempt it themselves)

65SpencerAve

2+ Year Member
Q=(v)(A) -> where Q is the flow rate, v is the velocity, and A is the area; since the question provides the diameter and not the area, you have to use 'pi/4 x diameter^2' in the equation for area: Q=(v)(pi/4 x diameter^2) [note: pi=3.14 ... don't know how to add the greek symbol for pi]

Cawolf

Medical Student
5+ Year Member
The above answer is the easiest, but if you forget, I always suggest to look at the units.

In this case we have m^3/s.

You are given velocity, so it makes sense to have the answer equal velocity x something.

Then, you are given the diameter of a supposedly round object. What can you determine with that?

The area, which is pi*r^2 = pi*(d/2)^2 = pi/4 * d^2 with units of m^2.

These multiply to give you the answer, but can be determined without knowing a formula.

Applicable to any unit-based question.