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I was asked the following question:

Consider a car that weights $2$ tons and that stands on the ground so the area of each tire on the ground is $150\, cm^2$. How much pressure the car has on the ground?

I not familiar with this type of questions. Usually, I know how much the car weights and I use the Newton's laws to calculate the pressure ($mg=N$). Does the writer of this question meant to calculate the force that the car has on the ground by the third Newton's law? Also, what does it mean that area of each tire is $150 cm^2$ and why it matters?

EDIT: Should the answer be as follows? $$ P=\frac{F}{A}=\frac{mg}{A}=\frac{2\cdot 10^3\cdot 9.8}{4\cdot 150\cdot 10^{-4}}=326666.666 $$

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  • $\begingroup$ What you wrote is Newton's law for force $ma=F$, where $m$ is mass, $a$ acceleration (or $g$ acceleration due to gravity) and $F$ is force. Pressure is force over area $\frac{F}{A}$, where $A$ is area. Does this help answer your question? $\endgroup$
    – Stratiev
    Commented Jun 7, 2020 at 13:28
  • $\begingroup$ @Stratiev Oh I didn't know this formula, thanks! But what considered the area? Is it $4\cdot 150$ because the car has $4$ tires? $\endgroup$
    – vesii
    Commented Jun 7, 2020 at 17:20
  • $\begingroup$ > the area of each tire on the ground is 150cm2. $\endgroup$
    – Stratiev
    Commented Jun 7, 2020 at 18:48
  • $\begingroup$ So the answer is $P=\frac{F}{A}=\frac{mg}{A}=\frac{2\cdot 10^3\cdot 9.8}{4\cdot 150\cdot 10^{-4}}=326666.666$? What are the units of pressure? Is it $N/ m^2$? $\endgroup$
    – vesii
    Commented Jun 7, 2020 at 19:21
  • $\begingroup$ You should always include the units in your calculation. $\frac{mg}{A}=\frac{2\cdot 10^3\ kg\cdot 9.8\ m/s^2}{4\cdot 150\cdot 10^{-4}\ m^2}=...$ Then you will automatically find the unit of the result. $\endgroup$
    – Thomas Fritsch
    Commented Jun 8, 2020 at 12:41

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