An 88 kg man sits in a 7 kg chair so that his weight is evenly distributed on the legs of the chair. Assume that each leg makes contact with the floor over a circular area with a radius of 1.5 cm. What is the pressure exerted on the floor by each leg?keep on getting this one wrong; I imagine you multiply the area times 4 because its 4 legs, and then once you've solved for everything divide by 4 again (to get the force on each leg).Enlighten me?
The area of each leg is π x r? = 3.142 x 1.5cm x 1.5cm. = 7.0cm? = 0.0007m?. The man plus chair total weight = Mass x 9.81m/s?. = 95kg x 9.81m/s? = 932 N. A Pressure of 1.0 Pascal = 1N/m?. 932N / 4 legs = 233N per leg. 233N / 0.0007m? = 332,839 Pa = 332.8kPa. per leg. (332.8kPa / 101.3kPa/atm) x 14.7psi/atm = 48.3psi.
Pressure is in kg/cm^2; your answer is in kg/1.5cm^2 if you didn't account for the fact that the radius of the contact area is more than 1cm.
Not sure what your problem is. The force on each leg is clearly: F= (88+7)/4 Kg The area of each leg is A= pi* R^2 cm2 where R=1.5 The pressure on each leg is p= F/A (kg/cm2)
The total mass of the chair and the man is: m = m1 + m2 = (88 kg) + (7 kg) = 95 kg So, the total weight, and thus the total force of the legs on the floor is: F = W = mg = (95 kg)(9.8 m/s^2) = 931 N The area of each leg is: A1 = pi*r^2 = pi(1.5x10^-2 m)^2 = 7.07x10^-4 m^2 So, the total area is: A = 4*A1 = 4(7.07x10^-4 m^2) = 2.83x10^-3 m^2 Thus, the pressure exerted by each leg is: P = F/A = (931 N)/(2.83x10^-3 m^2) = 3.29x10^5 Pa
