Force that pressure exerts on a dart?

Use the equation Pressure = Force / Area. Solve the equation for Force to get Force = Pressure * Area. Now, just plug in the values. Force = 0.006 Pa * (pi)0.008^2. Notice you need to divide the radius (0.008 m), not the diameter, in the equation for the area of a circle. The answer is 1.21 N.