Question

Which situation has the greatest pressure? A. Atmospheric pressure at sea level, equal to 1.01 X 105 N/m2 B. The pressure that a person of mass 70 kg exerts on the floor when she balances on the ball of one foot, with an area of contact of 50 cm2 C. The pressure that a physics textbook of mass 2.5 kg exerts on a desk when it is lying flat on the desk, with an area of contact of 22 cm X 28 cm

Answer 1

Answer:

The correct option is B

Explanation:

In part A pressure is given as $1.01*10^5 N/m$

In Part B we can calculate the pressure using the formula

        $P = \frac{F}{A}$

Where F is the force which in this case is weight which can be obtained as follow

            W = Mg

Substituting 70kg for M and $9.8m/s^2$ for g

              $W = 70 *9.8$

                  $=686N$

A is the area with a value $50cm^2 = \frac{50}{10000} = 5.0*10^{-3}m^2$

So substituting into the above equation

              $P = \frac{686}{5.0*10^{-3}}$

                  $= 1.37 *10^5 N/m^2$                      

for part c

    A  $= 22*28 cm^2= \frac{22*28}{10000}m^2$

          $=6.16*10^{-2}m^2$

     F  $= 2.5 * 9.8$

        $= 24.525N$

Therefore $P = \frac{24.252}{6.16*10^{-2}}$

                    $= 298 N/m^2$

From this we see that the value of P for part B is the greatest