A man weighing 785 N lies on a bed of nails.

Question

a) A man weighing 785 N lies on a bed of nails. Find the average pressure exerted by a nail on his skin if there are 1060 nails and the flattened point on each nail has a radius of 0.500 mm.



 (b) Calculate the pressure exerted on the skin by an acupuncture needle of radius 0.100 mm applied with a force of 6.00 N.

Answer 1

a) pressure = [Force (in Newtons)]/ [area (in square meters)]

Force= 785 N

Area= 1060*(pi)*r^2=1060*3.142*(5*10^-5m)^2   Note: 0.05mm=(5*10^-5=0.00005m)

 

b) pressure= Force/ area

Force= 6.00 N

area= pi*r^2=3.142*(1*10^-5m)^2