# Tag Info

7

You can absolutely have negative pressure in solids or liquids. Think of an elastic solid being forced to expand to to adhesion to the walls of some chamber. That has negative pressure even if the comparison is a total vacuum. Depending on the bulk modulus of the material being stretched and the strength of the interaction with the walls of the chamber ...

4

You're right, absolute pressure can't be negative. Of course, you can easily have a $20\: \mathrm{PSI}$ pressure differential (although not without pressure above $1\: \mathrm{ATM}$ since that's $14.22\: \mathrm{PSI}$ at sea level). Check out Wikipedia on the zero-reference: Absolute pressure is zero-referenced against a perfect vacuum, so it is ...

4

You know that you can pull a multiplicative constant out in front of an integral, right? $$\int cf(t)\mathrm{d}t = c\int f(t)\mathrm{d}t$$ where $f(t)$ is any function of $t$, like $t^2$ or $t(2\text{ s} - t)$ (and $c$ does not depend on $t$). Units can be part of that constant factor too. In this case, the constant factor is $4\mathrm{\ kg\ m/s^4}$. The ...

2

This probably is why it is useful to use variables. If we just let $q=4\,{\rm kg\,m/s^4}$ and $h=2\,{\rm s}$, then your force is $$\mathbf{F}=qt\left(h-t\right)\hat{\mathbf{i}}$$ We then integrate this over time $t$, $$\int_0^t\mathbf{F}\,dt'=q\int_0^tt'\left(h-t'\right)dt'\,\hat{\mathbf{i}}$$ we get,  ...

1

An angle in $rad$ is just a number and it is dimensionless. So drag coefficient has units $J.s$, $kT$ has units $J$ and $D_{rot}$ has units $s^{-1}$.

0

both M.k.S. and C.G.s. unit of temp. are kelvin as well as time has a same unit that is Sec.

Top 50 recent answers are included